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Table of Contents

1. Parallel Session - Spin Structure of Nucleons and Nuclei from Low to High Energy Scales ..... 1

2. Parallel Session - Spectroscopy-Status and Future Prospects .................................................. 2

3. Pre-conference .......................................................................................................................... 3

4. Main Conference....................................................................................................................... 5

5. Posters ...................................................................................................................................... 8

1

Parallel Session - Spin Structure of Nucleons and Nuclei from Low to High Energy Scales

Tuesday November 03

15:00-16:40 - Session I on High Energy Spin Structure Nucleon Spin Structure: overview Jen-Chieh Peng 30’+5’ JLab Spin Hall A & C Results Whitney Armstrong 20’+5’ RHIC Spin Results Oleg Eyser 20’+5’ Lattice Calculation of Polarized PDFs Fernanda Steffens 12+3’

17:00-18:05 - Session II on High Energy Spin Structure

Jefferson Lab Hall B Results Marco Cantalbrigo 20’+5’ Nuclear DVCS Nathan Baltzel 20’+5’ Deeply Pseudoscalar Meson Production and Generalized Transversity Distributions

Valery Kubarovsky

12+3’

Wednesday November 04

15:00-16:30 - Session I on Low energy spin structure

Overview of Low energy Spin Structure Function Experiments Jian-Ping Chen 30’+5’ Extraction of the Proton Spin Polarisabilities with Compton scattering

Cristina Collicot 20’+5’

New measurement of proton generalized polarizabilities by Virtual Compton Scattering at MAMI

Loup Correa

12+3’

Measurements and prospects on the Generalized Polarizabilities of the proton

Nikos Sparveris

12+3’

17:00-18:30 - Session II on Low energy spin structure

Polarizabilities and Sum Rules: New Vistas Vladimir Pascalutsa 20’+5’ Low Energy Spin Structure Functions: Chiral Perturbation Theory Results

Hermann Krebs

20’+5’

Lepton universality test in the photoproduction of e−e+ versus µ−µ+ pairs on a proton target

Vladyslav Pauk

12+3’

Hyperons and charmed baryons axial charges from lattice QCD Christos Kallidonis 12+3’

Thursday November 05

15:00-16:30 - Session on New Directions and Discussion

Drell-Yan Paul Reimer 20’+5’ EIC: Status Report on Glue and Sea Abhay Deshpande 20’+5’ PEPPo, a universal access to polarized positrons Eric Voutier 12+3’

2

Parallel Session - Spectroscopy-Status and Future Prospects Tuesday November 03

15:00-16:30- Session I on Charmonium Spectroscopy

XYZ states: BES-III Results Zhiqing Liu 25’+5’ Heavy flavored hadron spectroscopy at Belle and prospect Kenkichi Miyabayashi 25’+5’ Pentaquarks and exotic charm spectroscopy at LHCb Mike Williams 25’+5’

Wednesday November 04

15:00-16:30 - Session II on Charmonium Spectroscopy

Charm Spectroscopy from lattice QCD Graham Moir 20’+5’ ΧcJ e+e- decays within the effective theory approach Nikolay Kivel 20’+5’ Novel analysis method for excited states in lattice QCD Theodoros Leontiou 15’+5’ Two Unexpected Features of e+e- Annihilation: Imaginary Charmonium Decay Amplitudes Baryon Timelike Form Factors: an Update

Marco Destefanis 15’+5’

17:00-18:30 - Session I on Light Quark Spectroscopy

Lattice results for light quark hybrids David Wilson 30’+5’ Light Quark Spectroscopy Phenomenology Vincent Mathieu 25’+5’ COMPASS Results in Spectroscopy Jan Friedrich 20’+5’

Thursday November 05

15:00-16:30 - Session II on Light Quark Spectroscopy

Meson spectroscopy in Hall-B Raffaela de Vita 20’+5’ eta, eta' Physics Andrej Kupscz 20’+5’ Three-body Final State Interaction in eta -> 3pi Igor Danilkin 15’+5’

3

Pre-conference

Saturday October 31

18:00-21:30 - Frontiers and Careers in Photonuclear Physics

18:00-21:30 Session chair: Charlotte Van Hulse

Track reconstruction for the Olympus experiment Becky Russel

20’

Multidimensional analysis of the nuclear attenuation effect at HERMES

Gevorg Karyan

20’

The Nuclear Contacts, Photo-Disintegration and Momentum Distributions Ronen Weiss 20’

Exciting proton in muonic hydrogen Franziska Hagelstein 20’ How to write a good proposal/grant app & CV Martha Constantinou 60’

Sunday November 1, 2015

11:00 – 20:00 - Career building

11:00-12:00 - Session chair: Or Hen

Modelling nuclear scattering reactions in the intermediate energy regime

Wim Cosyn 60’

14:30 -16:30 - Session chair: Wim Cosyn

Modern data analysis techniques Mike Williams 60’ Physics in archaeology Eli Piasetzky 60’

17:00 – 20:00 - Session chair: Or Hen

The puzzling spin or the Spin Puzzle Charlotte Van Hulse 60’ Example of career path in the USA Mike Williams 60’ Example of career path in Europe Silvia Niccolai 60’

4

Monday November 2, 2015

09:00 – 20:30 - Introductory Lectures

09:00 -10:30 - Session chair: Rajan Gupta

Nuclear Physics Tests of Fundamental Symmetries Michael Ramsey-Musolf

60’

11:00 -13:00 - Session chair: Giannis Koutsou

Introduction to Lattice QCD Rajan Gupta 60’ From outer space to deep inside: exploring neutron skins of nuclei

Concettina Sfienti 60’

15:00-16:40 - Session chair: Charlotte Van Hulse

Introduction to in-medium nucleon properties Or Hen 60’ Pion Form Factor Measurement at BESIII Martin Ripka 20’ Two-photon exchange corrections in elastic lepton-proton scattering at small momentum transfer

Oleksandr Tomalak 20’

17:10-18:10 - Session chair: Or Hen

Evaluation of the forward Compton scattering off protons Oleksii Gryniuk 20’ A focusing DIRC detector for GlueX John Hardin 20’ Proton Polarizabilities review by a student Loup Correa 20’

5

Main Conference Tuesday November 3, 2015

09:00 – 10:30 – Overview

Session chair: Constantia Alexandrou

Recent Results and Experimental Developments in Hadronic Physics

Bernd Surrow 40’+5’

Lattice QCD and its interface to phenomenology Stephan Durr 40’+5’ 11:00 – 13:00 - Dark matter/astro

Session chair: Niklaus Berger

Recent Results of the Alpha Magnetic Spectrometer on the International Space Station

Alberto Oliva 40’+5’

Gamma-ray astronomy - exploring the most extreme places in the Universe

Christian Stegmann 40’+5’

From outer space to deep inside: exploring neutron skins of nuclei

Concettina Sfienti 25’+5’

Wednesday November 4, 2015 09:00 – 10:30 - BSM: Low energy precision physics

Session chair: Michael Ramsey-Musolf

New Physics Searches With Muons Andrzej Czarnecki 40’+5’ Proton/electron EDM in storage rings Yannis K. Semertzidis 40’+5’

11:00 – 13:15 - Precision electroweak/Cosmology

Session chair: Yannis Semertzidis

Neutrino Physics Robert McKeown 40’+5’

Electroweak Baryogenesis Michael Ramsey- Musolf

25’+5’

The Qweak Experiment: A Direct Measurement of the Weak Charge of the Proton

Dipangkar Dutta 25’+5’

The search for Dark Matter Constantinos Skordis 25’+5’

6

Thursday November 5, 2015 09:00 – 10:30 - Form factors, GPDs, etc

Session chair: Jian-Ping Chen

Experimental studies of Generalized Parton Distributions Sylvia Niccolai 25’+5’ Theoretical status of the nucleon spin Marc Schlegel 25’+5’ The OLYMPUS Experiment Axel Schmidt 25’+5’

11:00 – 13:00 - GPDs, DVCS , TMDs, proton radius, etc

Session chair: Marc Vanderhaeghen

Longitudinal spin strucuture of the proton- RHIC and COMPASS results

Fabienne Kunne 25’+5’

Hadron structure from lattice QCD: current status and future perspectives

Giannis Koutsou 25’+5’

Status of the proton charge radius puzzle Aldo Antognini 25’+5’ Proton radius measurements and future prospects Miha Mihovilovic 25’+5’

17:00 – 18:00 Oral presentations of three best posters

Friday November 6, 2015 09:00 – 10:30 - Meson and baryon spectroscopy/exotics

Session chair: Reihard Beck

Recent results from BESIII Yangheng Zheng 40’+5’ Experiment GlueX at Jefferson Lab Eugene Chudakov 40’+5’

11:00 – 13:00 - Spectroscopy/Few body/Nuclear Effects

Session chair: Yangheng Zheng

Spectroscopy in the charm range: from BESIII to PANDA Stefano Spataro 25’+5’ Hypernuclear physics at KEK-PS and J-PARC Kazuma Nakazawa 25’+5’ Baryon Spectroscopy: Recent Results and Impact Reinhard Beck 25’+5’ Atomic nucleus from QCD on lattice Takashi Inoue 25’+5’

7

Saturday November 7, 2015 09:00 – 12:30 - Summary of workshops, Future

09:00 – 10:30 - Session chair: Zein-Eddine Meziani

Summary I (Workshop I: Spin low to high Q2) Jen-Chieh Peng 40’+5’ Summary II (Workshop II: Spectroscopy) Eberhard Klempt 40’+5’

11:00 – 12:30 - Session chair: Bernd Surrow

Electron scattering in Mainz: Plans for the next decade Niklaus Berger 40’+5’ A New High Energy Electron Microscope for Precision Study of QCD

Richard G. Milner 40’+5’

Sum

8

Posters

1 Neutron Photo-Pion Amplitudes and Quasi-free Neutral Pion Photo-production from Deuterium in the Threshold Region

Hannah Stegen

2 Background Simulations for Experimental Extraction of Neutron Scalar Polarizabilities via Compton Scattering

Meg Morris

3 The Nuclear Contacts, Photo-Disintegration and Momentum Distributions Ronen Weiss 4 Status of the DarkLight Experiment Charles Epstein 5 Beam tests for the 2015 PANDA Barrel DIRC prototype at CERN Marvin Krebs 6 The gluon moment from twisted mass lattice QCD Christian Wiese 7 Monte Carlo simulation and event generators for OLYMPUS Jan Bernauer

8 Nucleon structure with lattice QCD simulations at physical value of the pion mass

Martha Constantinou

9 Systematic Uncertainties in the OLYMPUS Experiment Lauren Ice 10 The "BaBar-Puzzle": What remains and why it is important Nils Offen 11 Hyperon and charmed baryon axial charges from lattice QCD Christos Kallidonis 12 A focusing DIRC detector for GlueX John Hardin 13 Track reconstruction for the OLYMPUS experiment Rebecca Russell

14 Model Independent extraction of Multipole Amplitudes from a combined analysis of p(γ,π+)π0 and p(γ, π+)n data

Lefteris Markou

15 Future Measurements of the Nucleon Elastic Electromagnetic Form Factors at Jefferson Lab

Gerard Gilfoyle

16 Nucleon spin structure functions in chiral perturbation theory Franziska Hagelstein

17 Tagged spectator DIS off the deuteron as a tool to extract neutron structure

Wim Cosyn

18 Timelike Compton Scattering off the neutron Marie Boer 19 Evaluation of the forward Compton scattering off proton Oleksii Gryniuk

20 An Improved Limit for Gamma_ee of X(3872) and Gamma_ee Measurement of psi(3686)

Martin Ripka

21 Two-photon exchange corrections in elastic lepton-proton scattering at small momentum transfer

Oleksandr Tomalak

22 Pion Photoproduction Studies at MAMI Philippe Martel

23 The Neutron Electric Dipole Moment from lattice QCD Andreas Athenodorou

24 Dilepton pair production in NA61/SHINE experiment Joanna Stepaniak 25 Search for Tetraquark J^P = 0^+ Candidates by using Lattice QCD Jacob Finkenrath

26

Hadron multiplicity ratios in semi-inclusive deep-inelastic scattering have been measured on neon, krypton and xenon targets relative to deuterium using the 27.6 GeV beam of HERA at the HERMES experiment. They are presented for pions (π+, π-), kaons (K+,

Gevorg Karyan

27 Analysis of e+e−→ nn ̄ from 2015 Scan Data at BESIII Samer Ahmed

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9

Parallel Session RHIC Spin Results O. Eyser The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is the world's only polarized proton collider with center-of-mass energies up to 500 GeV and polarizations of about 60% for each proton beam. It provides unique opportunities to study the spin structure in hadronic systems and opens new kinematic regions compared to deep inelastic scattering. The three pillars of the RHIC spin program cover the gluon polarization, sea quark helicity distributions, and transverse spin effects in hadronic systems. We will summarize recent results and discuss near term plans and their implications on parton distribution functions in the collinear and transverse momentum dependent frameworks.

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10

Parallel Session

Lattice Calculation of Polarized Parton Distributions

C. Alexandrou, K. Cichy, V. Drach, K. Hadjigiannakou, K. Jansen, F. Steffens, C. Wiese

We report on our exploratory study for the direct evaluation of the x dependence of nonsinglet polarized parton distribution functions directly from lattice QCD, based on a recently proposed new approach by Xiangdong Ji. We present encouraging results using Nf = 2 + 1 + 1 twisted mass fermions with a pion mass of about 370 MeV and a 323 X 64 lattice. The calculation is done for a nucleon moving in the third direction with momentum P3 = 1, 2 and 3 in units of 2Π/L. In addition, we use 0, 2 and 5 steps of HYP smearing in order to estimate the influence of the of the Wilson line renormalization, which is yet to be done. We also estimate, using an extrapolation to high values of momentum, what would be the result for a calculation using P3= 4. The results, after applying nucleon mass corrections to the distributions, are extremely encouraging and promising.

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11

Parallel Session

Deeply pseudoscalar meson production and Generalized Transversity Distributions

V. Kubarovsky

A longstanding goal in nuclear and particle physics has been to describe the three dimensional structure of the nucleon in terms of the quarks and gluon elds. Exclusive electron scattering at high momentum transfers Q2 directly related to the Generalized Parton Distributions (GPDs). Most reactions studied, such as DVCS or vector meson electroproduction, are primarily sensitive to the chiral-even GPDs. Very little is known about the chiral-odd GPDs, except that HT becomes the transversity function h1 in the forward limit. It turns out that pseudoscalar meson electroproduction, and especially π0 and η production, were identied as especially sensitive to the parton helicity-flip subprocesses. Dedicated experiments to study Deeply Virtual Meson Production have been carried out in Hall B at Jefferson Lab. The cross sections and asymmetries of the exclusive pseudoscalar meson electroproduction processes in a very wide kinematic range of Q2, xB and t have been measured with CLAS. The Generalized form factors < HT >π.η and < ĒT > π.η were extracted directly form the experimental observables. These combined π0 and η data will provide the way for the flavor decomposition of the transversity GPDs.

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12

Parallel Session

Extraction of the Proton Spin Polarisabilities with Compton scattering

C. Collicott

Nucleon polarisabilities are fundamental structure observables, like the nucleon mass or charge, which are sensitive to the internal quark dynamics of the nucleon. Spin dependent terms of the nucleon polarisabilities quantify the response of the proton's spin to an applied electromagnetic field. The

leading order polarisabilities, denoted by γ E1E1, γ M1M1, γ E1M2, and γ M1E2, quantify the spin response to electric and magnetic dipole and quadrupole interactions. Despite signi_cant theoretical interest in the proton spin polarisabilities - including calculations from dispersion theory, K-matrix theory, and chiral perturbation theories | very little experimental information exists. Polarised Compton scattering off the proton can be used to study the polarisabilities of the proton, thus probing the internal structure of the proton. The A2 Collaboration, a real photon facility in Mainz, Germany, is conducting an experimental program to extract the proton spin polarisabilities from real Compton scattering. Details of this experimental program, along with the first extraction of the proton spin polarisabilities, will be presented.

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13

Parallel Session

New measurement of proton generalized polarizabilities by Virtual Compton Scattering at MAMI

L. Correa

This talk proposes to present the preliminary results of a Virtual Compton Scattering (VCS) experiment done at MAMI (Mainz, Germany). It reports on the new measurements of the generalized electric and magnetic polarizabilities (GPs) αE and βM , which are fundamental quantities describing the proton deformation in an applied electromagnetic field. The GPs depend on Q2, the virtuality of the photon probe. These observables are accessed via the photon electroproduction process ep ep in the low-energy regime at a fixed Q2. In the last 20 years several experiments at MAMI, Bates and JLab have shown a non-trivial Q2-behaviour of the GPs, especially in the domain around Q2 = 0.3 GeV2. The analyzed data were collected with the Mainz Microtron from 2011 to 2015 in the range of interest, i.e. at Q2 : 0.1, 0.2 and 0.5 GeV2. The purpose of these new measurements is to better understand the GPs behaviour at low Q2.

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14

Parallel Session

Measurements and prospects on the Generalized Polarizabilities of the proton N. Sparveris

The Generalized Polarizabilities (GPs) are fundamental quantities of the nucleon, sensitive to both the role of the quark and pion degrees of freedom, and as such they are extremely valuable for a deeper understanding of the nucleon structure. The GPs can be explored through Virtual Compton Scattering and, contrary to the elastic form factors, are sensitive to all the excited spectrum of the nucleon. Recent results from MAMI as well as future prospects at JLab will be discussed.

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15

Parallel Session

Lepton universality test in the photoproduction of e−e+ versus µ−µ+ pairs on a proton target

V. Pauk

In view of the significantly different proton charge radius extracted from muonic hydrogen Lamb shift measurements as compared to electronic hydrogen spectroscopy or electron scattering experiments, the photoproduction of a lepton pair on a proton target in the limit of very small momentum transfer is considered as away to provide a test of the lepton universality when extracting the proton charge form factor. It is shown, that by detecting the recoiling proton in the γp → l+l-p reaction, a measurement of a ratio of e−e+ + μ−μ+ over e−e+ cross sections with a relative precision of around 2 % would allow for a test to distinguish between the two different proton charge radii currently extracted from muonic and electronic observables.

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16

Parallel Session

PEPPo, a universal access to polarized positrons

E. Voutier

Positron beams, both polarized and unpolarized, have been dentified as essential ingredients for the experimental program at the next generation of lepton accelerators. In the context of the Hadronic Physics program at the Thomas Jefferson National Accelerator Facility( Jefferson Lab), positron beams are complementary to mandatory tools for the understanding of the electromagnetic structure of the nucleon, in both the elastic and the deep-inelastic regimes. A proof-of-principle experiment for a new method to produce polarized positrons has recently been performed at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e+e− pairs from the polarized bremsstrahlung radiation produced by a longitudinally polarized electron beam. The experiment was performed at the injector of the Continuous Electron Beam Accelerator Facility at Jefferson Lab and investigated the polarization transfer of 8.3 MeV/c polarized electrons to positrons produced in varying production target thicknesses. A dedicated new beam-line was constructed to produce, collect and transport positrons in the momentum range 3.2-6.2 MeV/c, and deliver them to a polarized iron target for polarization measurements. This technique validates a new pathway that opens a world-wide access to polarized positrons. This talk will discuss the physics motivations for polarized positron beams at Jefferson Lab and measurements of the polarization transfer in the production of polarized positrons induced by polarized electrons. The PEPPo experimental setup, principle of operation, and experimental results will be presented.

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17

Parallel Session

XYZ states: results from BESIII

Z. Liu

Searching for exotic states (XYZ states) with quark content different from conventional baryons and mesons are of high interest in particle physics. Using the large e+e- data samples collected above 4 GeV, the BESIII experiment was able to study the XYZ states in an unique way. In 2013, BESIII has discovered the charged charmoniumlike states Zc(3900), and later on Zc(4020)=Zc(4025), which are obviously good candidates for four quark states. The corresponding neutral candidates of them are also observed by BESIII with more data later, and thus, iso-spin triplet of Zc(3900), Zc(4020)=Zc(4025) are well established. To probe the nature of XYZ states, BESIII also studied their properties by investigating different decay channels, such as Y (4260) π± Zc(3885) π± (D D¯ *)∓, Y (4260) γX(3872) and so on, doing more precise measurement for their parameters, such as mass, width and spin-parity. In this talk, I’ll review the recent results of XYZ states from BESIII, and discuss the future prospects of XYZ physics at BESIII., after applying nucleon mass corrections to the distributions, are extremely encouraging and promising.

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18

Parallel Session

Heavy flavored hadron spectroscopy at Belle and prospect

K. Miyabayashi

Observations of the quarkonium-like exotic hadrons which are so-called "XYZ" as well as charm baryons at Belle are reviewed. Attempting to give interpretation for those particles reveal the picture of fundamental degree of freedom to describe hadrons. Limitation with current statistics and future prospect in the upgraded experiment of Belle II are also discussed.

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19

Parallel Session

Pentaquarks and exotic charm spectroscopy at LHCb

M. Williams

I will discuss the major contributions to exotic charm spectroscopy made by the LHCb experiment at CERN using data from Run 1 at the LHC. The focus of this talk will be the discovery of states consistent with pentaquarks; however, I will also briefly discuss tetraquarks and other areas of exotic spectroscopy, including the X(3872) state.

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20

Parallel Session

Charm Spectroscopy from Lattice QCD

G. Moir

The past decade has seen the emergence of a plethora of theoretically unexplained charmonium-like states; the so-called 'X, Y, Z's'. Using the latest techniques, lattice calculations have made rapid progress towards understanding the spectrum of mesons containing charm quarks. In this talk I will review recent state-of-the-art calculations of highly excited spectra, exotic and hybrid charmonium-like states as well as present first steps toward robust scattering calculations in the charm sector of QCD.

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21

Parallel Session

ΧcJ e+e- decays within the effective theory approach

N. Kivel, M. Vanderhaeghen

The width for ΧcJ e+e- decay is computed within the effective theory framework. The amplitude of the process is factorized on the short and long distance contributions using non-relativistic QCD effective theory (NRQCD). After integration over hard modes the leading-order amplitude is described by two contributions which are associated with the two different domains in the electromagnetic loop integral describing the two-photon annihilation of theheavy quark-antiquark pair. Corresponding operators are rigorously defined in the framework of NRQCD. The contribution with two hard photons is reduced to the soft matrix element which is expressed through the derivative of charmonium wave function at the origin. Corresponding value is well know and has been computed in various potential models. The second contribution describes configuration with ultrasoft photon and have not been considered before. In order to estimate its value we use low energy effective theory known as heavy hadron chiral perturbation theory. This allows us to get the value of the unknown matrix element in a model independent way. We obtain that the value this contribution is numerically large giving the dominant numerical effect. The obtained estimates for decay widths are 0:084 eV and 0:16 eV for Xc1 and Χc2, respectively.

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22

Parallel Session

Novel analysis method for excited states in lattice QCD

T. Leontiou, C. Alexandrou, C. Papanicolas, S. Stiliaris

We employ a novel method to analyze Euclidean correlation functions entering the calculation of hadron energies in lattice QCD. The method is based on the sampling of all possible solutions allowed by the spectral decomposition of the hadron correlators. AMIAS (Athens Model Independent Analysis Scheme) uses importance sampling to probe the correct minimum of the multidimensional space defined by the states of the correlation matrix and determines the number of excited states, which can be extracted from the information that the lattice data encode. It takes advantage of the whole time dependence of the correlators not requiring identification of the large time asymptot that limits the accuracy of the determination of excited states. We demonstrate the applicability of the method by studying the nucleon excited states in the positive and negative parity channels over a pion mass range of about 400 MeV to 150 MeV. The method successfully extracted the first excited states in the positive and negative parity nucleon channels, identifying the Roper in the positive parity channel. In the negative parity apart from the first excited state the Nπ scattering state was also observed. The results are compared to the standard variational approach routinely used to study excited states within lattice QCD. The main advantage of our new approach is its ability to unambiguously determine all excited states for which the Euclidean time correlation function is sensitive on. Insensitive parameters (amplitudes and/or masses) are easily identified and do not bias the quality of the results.

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23

Parallel Session

Two Unexpected Features of e+e- annihilation Imaginary Charmonium Decay Amplitudes Baryon Timelike Form Factors: an Update R. Baldini Ferroli, S. Pacetti, M. Destefanis

Experimental data on the relative phase between strong and e.m. J/y decay amplitudes suggest that the strong amplitudes are purely imaginary and not real, as it would be expected. A quarkonium model, based on an old suggestion by Freund and Nambu, is presented, in the attempt to explain this unexpected feature. A possible test of this model at a p pbar collider is shown. The puzzling present data on the relative phase between strong and e.m. (2S)decay amplitudes are reviewed. An update of the Baryon Timelike Form Factors, close to the various threshold, is also presented, showing features that might challenge so far undisputed assumptions.

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24

Parallel Session

COMPASS Results on Spectroscopy

J. Friedrich

With the COMPASS experiment at the CERN Super Proton Synchrotron, properties of hadrons are investigated through high-energy muon and hadron scattering. In the program with hadron beams, hadron resonances are studied in partial-wave analyses in diffractive and central-production reactions. Interesting possible hadronic states are exotics such as hybrid and glueball states. COMPASS contributes since several years, exploiting high-statistics data sets on pion and proton reactions on proton and nuclear targets with various multi-hadronic final states. Results on such states, as well as the recent observation of the narrow a1(1420), will be discussed.

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25

Parallel Session

Three-body Final State Interaction in eta -> 3pi

I. Danilkin

We present an unitary dispersive model for the η 3π decay process based upon the Khuri-Treiman equations which are solved by means of the Pasquier inversion method [1]. The description of the hadronic final-state interactions for the η 3π decay is essential to reproduce the available data and to understand the existing discrepancies between Dalitz plot parameters from experiment and chiral perturbation theory. Our approach incorporates substraction constants that are fixed by fitting the recent highstatistics WASA-at-COSY data for ηπ+ π- π0. Based on the parameters obtained we predict the slope parameter for the neutral channel to be α = −0.022 ± 0.004. Through matching to next-to-leading order chiral perturbation theory we estimate the quark mass double ratio to be Q = 21.4 ± 0.4. References [1] P. Guo, I. V. Danilkin, D. Schott, C. Fernndez-Ramrez, V. Mathieu and A. P. Szczepaniak, arXiv:1505.01715 [hep-ph] (Phys. Rev. D in press), 2015.

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26

Talks

The Nuclear Contacts, Photo-Disintegration and Momentum Distributions

R. Weiss, N. Barnea, B. Bazak

A new variable, called the contact, was introduced recently by S. Tan for systems of two component fermions. In our work we generalize the definition of the contact for nuclear systems and use it to study different properties of nuclei, such as short-range correlations and photo nuclear reactions. In ultra cold atomic systems, Tan's contact measures the probability to find two atoms close together and is connected to many properties of the system, such as its energy, pressure and the high momentum tail of the momentum distribution of the atoms. These relations were proved both experimentally and theoretically. The aim of our work is to generalize the definition of the contact to nuclear systems and to use it for finding new and interesting relations between nuclear quantities. So far we have successfully defined the matrices of nuclear contacts and connected them to both the quasi-deuteron (qd) photo-disintegration model and to the high momentum tail of the nucleon momentum distributions. In the generalized definition of the contact, we have taken into consideration all partial waves and finite-range interactions. Regarding the photo-disintegration, we have reformulated Levinger's qd model, resulting a relation between the Levinger constant and the nuclear neutron-proton contacts. For the high momentum tails, we have obtained relations between the contacts and the one-nucleon and the two-nucleon momentum distributions. As a result, we have obtained an asymptotic relation between these two momentum distributions. This relation emphasizes the important contribution of two-body short-range correlations to the high momentum tail and was verified using available Variational Monte Carlo numerical data. Using this numerical data we have also obtained a very good correspondence between our two independent relations (the qd relation and the momentum relations). The numerical data was also used to study more properties of the nuclear contacts, including their scaling along the nuclear chart. The nuclear contacts seem to become a useful tool for studying different properties of nuclear systems. In future works we plan on expanding the contact relations to more aspects of nuclear systems. References: 1. R. Weiss, B. Bazak and N. Barnea, Phys. Rev. Lett. 114, 012501 (2015). 2. R. Weiss, B. Bazak and N. Barnea, arXiv: 1503.07047 [nucl-th] (2015).

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27

Talks

Modelling nuclear scattering reactions in the intermediate energy regime W. Cosyn We present work on a model used to describe the process of tagged spectator DIS o. the deuteron. The model uses a factorized approach and includes the effect of final-state interactions at intermediate to large Bjorken x through effective rescattering amplitudes of the produced hadrons X with the “spectator” nucleon. Comparisons with recent Jefferson Lab data are shown and discussed, also for the inclusive DIS case. We discuss the pole extrapolation method applied to the tagged spectator DIS process. This approach is based on the extrapolation of the measured cross sections at different momenta of the detected spectator proton to the non-physical pole of the bound neutron in the deuteron. The advantage of the method is that it makes it possible to suppress nuclear effects in a maximally model independent way. We apply the method to the recently measured BONuS data to extract the unpolarized neutron structure function at large x, and obtain a surprising x dependence at x = 0.6, indicating the possibility of a rise in the neutron to proton structure function ratio. We discuss applications of the method at a possible EIC, both for the unpolarized and polarized case.

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28

Talks

Modern data analysis techniques

M. Williams This lecture will focus on modern data analysis methods. Topics will include: machine learning; information and decision theory; resampling; multivariate goodness-of-fit and non-parametric regression; limit setting; etc. I will focus on the key aspects of each topic and give some examples of use in particle physics. I will also provide references for further reading and discussion.

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29

Talks

Nuclear Physics Tests of Fundamental Symmetries

M. Ramsey-Musolf

Nuclear physics tests of fundamental symmetries provide powerful probes of possible physics beyond the Standard Model. In this lecture, I review the motivation for beyond these searches; provide an overview of the key directions being pursued in nuclear physics fundamental symmetry tests; and discuss their complementarity with searches being performed at the high energy frontier.

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30

Talks

Introduction to In-Medium Nucleon Properties

O. Hen

The inelastic structure function of the nucleons is one of the most fundamental properties of QCD. Results from experimental studies of Deep-Inelastic Scattering (DIS) of unpolarized leptons off nucleons bound in nuclei suggest that their structure might be modified as compared to that of free nucleons. Detailed studies of this modification show that it increase with A, the nuclear mass number, show that its linearly proportional to the number of Two-Nucleon Short-range correlated (2N-SRC) pairs in nuclei. The latter are pairs of nucleons with high relative momentum and low center of mass momentum where high and low are relative to the Fermi momentum of the nucleus. This talk will overview experimental studies of structure function measurements and short-range correlations in nuclei. We will discuss the connection between the two and present future experiments that can help gain insight to its physical origin.

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31

Talks

Recent Results and Experimental Developments in Hadronic Physics B. Surrow

Quantum Chromodynamics (QCD) was developed as the fundamental theory of strong interactions. QCD describes hadrons as consisting of point like electrically charged quarks bound via color forces by the exchange of gluons. Properties of hadrons such as their mass and spin are emergent through the complex structure of the QCD vacuum. Momentum distributions of quarks and gluons in the nucleon are characterized by a large rise at low x which reflects the fact that the virtual particles of QCD are playing a dominant role. Understanding the structure and properties of the nucleon in terms of QCD drives experiments to high energies where the dominant, virtual particles at low x can be accessed and studied. The density of gluons inside a nucleon, which dominate over the sea quarks, must eventually saturate to avoid the violation of unitarity. Thus far, a saturated gluon density regime has not been conclusively observed. The understanding of basic properties of the nucleon such as its spin, as well as fundamental processes or hadronization that connects the experimental world of hadrons with the quarks and gluons of QCD, require new experimental insight. A highly desirable goal in understanding QCD is to develop a unified visualization of the subatomic world. In this regard, a major goal of current research is to carry out spatial imaging or tomography of the nucleon. Recent, selected results and future experimental developments concerning the nucleon structure and dynamics will be presented focusing on the research programs at COMPASS, JLAB and RHIC Spin followed by an outlook concerning a future Electron-Ion Collider facility.

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Talks

Lattice QCD and its interface to phenomenology

S. Durr

An overview is given of recent efforts in Lattice QCD to calculate observables of interest to phenomenology. I will discuss low-energy constants in ChPT and quark masses with an eye on the selection criteria used in the ongoing FLAG effort. In addition I will say a few words about light/charm decay constants and form factors, and add a few pointers to nuclear/meson structure calculations.

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Talks

Recent Results of the Alpha Magnetic Spectrometer on the International Space Station A. Oliva AMS-02 is a wide acceptance, high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. With a collection rate of approximately 1.7×1010 events/year, and thanks to the particle identification capabilities of 5 independent detectors, AMS is able to accurately measure all the charged cosmic rays (CRs) species separating hadrons from leptons, matter from anti-matter and determining the CRs chemical and isotopic composition. AMS-02 collaboration has recently released a first set of precise measurements of cosmic ray fluxes of positrons, electrons and protons detected in the GV to TV rigidity (momentum/charge) range. These results as well as preliminary results for anti-protons to protons ratio and CRs nuclear component fluxes and ratios (He, Li, B/C) will be shown and discussed.

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Talks

Gamma-ray astronomy - exploring the most extreme places in the Universe C. Stegmann

Recently ground based gamma-ray experiments have revealed a large variety of sources of gamma rays with energies in the TeV range which are among the most extreme places in our Universe. Gamma-ray sources allow to study processes capable of accelerating particles to energies orders of magnitude beyond the energies achievable with Earth based accelerators. The sources range from the remnants of supernova explosions in our own galaxy to supermassive black holes in the center of active galactic nuclei. In the presentation I will give an overview of the experimental status of the field together with an outlook into the near future.

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Talks

From outer space to deep inside: exploring neutron skins of nuclei C. Sfienti

An accurate determination of the thickness of the neutron skin of a nucleus would provide a unique experimental constraint on the density dependence of the symmetry energy of the nuclear EOS. A variety of experimental techniques to determine the neutron skin has thus been carried out over the last years. To overcome strong model dependencies a simultaneous combination of different techniques is mandatory. Combining high precision measurements using parity violating electron scattering with the opportunity to measure a multitude of nuclei given by coherent pi0 photoproduction allows a systematic determination across the periodic table thus benchmarking modern calculation. Status and prospects of the program at the MAMI and MESA accelerators at Mainz will be discussed.

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Talks

New Physics Searches With Muons A. Czarnecki I will review the various ways in which muons are being employed as probes for New Physics. After briefly summarizing past results, including the muon anomalous magnetic moment and the rare-decay searches, I will focus on future opportunities, notably the muon-electron conversion near a nucleus, the decay μ eee, the role of muonium spectroscopy, and the search for the true muonium, the muon-antimuon bound state.

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Talks

Neutrino Physics

R. McKeown

The last fifteen years has seen remarkable progress in the study of neutrinos, culminating in the award of the 2015 Nobel prize in physics. The experimental landscape for neutrino physics includes reactor experiments, long baseline accelerator studies, and searches for neutrinoless double beta decay. I will review recent progress, current status, and future prospects for this very active field.

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Talks

Electroweak Baryogenesis

M. Ramsey-Musolf

Electroweak baryogenesis is one of the most theoretically attractive and experimentally testable scenarios for explaining the origin of the cosmic matter-antimatter asymmetry. I discuss recent developments in this area and prospects for experimental tests using low-energy searches for permanent electric dipole moments and new particle searches at the Large Hadron Collider.

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Talks

The Qweak Experiment: A Direct Measurement of the Weak Charge of the Proton D. Dutta

The Qweak experiment, which ran in Hall C at Jefferson Lab from 2010-2012, measured the parity-violating asymmetry in elastic electron-proton scatter-ing at a small four-momentum transfer squared of <Q2 >=0.025(GeV/c)2 . The parity-violating asymmetry arises from the interference between the pho-ton and Z0-boson exchange amplitudes, and at low momentum transfers it is proportional to the weak charge of the proton, P

WQ The running of the weak mixing angle (sin2θW ), and thus the weak

charge PWQ , is potentially sensitive to new physics beyond the Standard Model. The projected

preci-sion for the full data set will result in sensitivity to new physics at the TeV scale, complementing searches at the Large Hadron Collider. The Qweak experiment has made the first determination of the weak charge of the proton using the data collected during the commissioning period, about 4% of the total data. The P

WQ was extracted in combination with data from earlier higher Q2 parity-violating electron-scattering experiments and state-of-the-art theoretical calculations, that help constrain hadronic effects. This talk will present the initial results and will discuss the status of the analysis of the full data set, as well as several ancillary measurements. This work is supported by the U.S. Department of Energy under contract number DE-FG02-07ER41528.

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Talks

The search for Dark Matter C. Skordis The biggest long-standing problem of modern cosmology is the nature of the Dark Matter. Dark Matter is a hypothetical constituent of the Universe which is postulated in order to fit current cosmological observations from the scales of galaxies, to galaxy clusters and the Cosmic Microwave Background (CMB). In this talk I will give a brief overview of the observations leading to the assumption of Dark Matter and then discuss the various efforts carried out in order to detect the particle responsible.

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41

Talks

Experimental studies of Generalized Parton Distributions

S. Niccolai Generalized Parton Distributions (GPDs) are nowadays the object of an intense effort of research, in the perspective of understanding nucleon structure. They describe the correlations between the longitudinal momentum and the transverse spatial position of the partons inside the nucleon and they can give access to the contribution of the orbital momentum of the quarks to the nucleon spin. Deeply Virtual Compton scattering (DVCS), the electroproduction on the nucleon, at the quark level, of a real photon, is the process more directly interpretable in terms of GPDs of the nucleon. Depending on the target nucleon (proton or neutron) and on the DVCS observable extracted (cross sections, target- or beam-spin asymmetries,...), different sensitivity to the various GPDs for each quark flavor can be exploited. This talk will be focused on recent promising results, obtained at Jefferson Lab, on cross sections and asymmetries for DVCS, and their link to the Generalized Parton Distributions. These data have opened the way to a “tomographic” representation of the structure of the nucleon, allowing the extraction of transverse-space densities of the quarks at fixed longitudinal momentum. The extensive experimental program to measure GPDs at Jefferson Lab with the 12-GeV-upgraded electron accelerator and the complementary detectors that will be housed in three experimental Halls (A, B, C), will also be presented.

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42

Talks

Theoretical status of the nucleon spin

M. Schlegel A brief overview is given on selected topics that concern the theoretical description of polarized hard scattering processes. A nucleon polarization that is longitudinal to its direction of motion is important as it gives insight into the helicity structure of partons in the nucleon. In addition, the situation where the nucleon is transversely polarized is discussed for some hard processes. New information about the spin structure of the nucleon can be extracted from these processes where a theoretical framework beyond the conventional collinear leading twist picture is needed.

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Talks

The OLYMPUS Experiment

A. Schmidt The OLYMPUS experiment was carried out to test the hypothesis that hard two-photon exchange (TPE) is responsible for the proton elastic form factor ratio discrepancy. The signature of TPE is the magnitude and kinematic dependence of the ratio of positron-proton and electron-proton elastic scattering cross sections. OLYMPUS data taking at DESY, Hamburg, Germany was completed in early 2013. Elastic scattering of 2 GeV electron and positron beams from a windowless gaseous hydrogen target internal to the DORIS storage ring was measured over a large scattering-angle range. Leptons and protons were detected in coincidence in a toroidal magnetic spectrometer. The luminosity was measured with redundant systems: a pair of tracking telescopes monitored the forward elastic rate, and a pair of calorimeters monitored the rate of symmetric MØller/Bhabha scattering. Over 4 fb-1

of data were collected, giving OLYMPUS excellent statistical precision. The latest results from the analysis will be presented and discussed in the context of the recent Novosibirsk and Jefferson Lab TPE experiments.

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Talks

Longitudinal spin strucuture of the proton- RHIC and COMPASS results F. Kunne Results on the longitudinal spin structure of the nucleon from both RHIC and CERN will be presented. Using the only polarized proton proton collider in the world, the STAR and PHENIX experiments at RHIC have placed stringent constraints on the helicity distributions of gluons and light quarks and anti-quarks in the polarized proton using jet, pi0 and W,Z probes at center-of-mass energies of up to 500 GeV. Using the 160-200 GeV polarized muon beam from CERN, the COMPASS experiment performs a rich program in inclusive and semi-inclusive deep inelastic scattering off longitudinally polarised nucleons. Results on the proton longitudinal spin structure function and a global NLO QCD fit, a verification of the Bjorken sum rule, gluon helicity and also quark fragmentation functions extracted from pion and kaon multiplicities will be shown.

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Talks

Hadron structure from lattice QCD: current status and future perspectives G. Koutsou Hadron structure calculations on the lattice have entered a new phase now that simulations at the physical values of the quark masses have become possible. In this talk, a review of recent hadron structure results from the lattice will be given, with emphasis on nucleon structure using simulations with physical or near physical quark masses. Recent results on the electromagnetic structure of the nucleon, the axial, scalar and tensor charges, as well as moments of generalized parton distributions will be presented, followed by an outlook towards lattice hadron structure calculations which can impact new physics searches.

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Talks

Status of the proton charge radius puzzle A. Antognini By performing laser spectroscopy of atomic transitions in muonic hydrogen we have determined the proton charge radius 20 times more precisely han previously obtained from electron-proton scattering and hydrogen high-precision laser spectroscopy. Yet our values disagrees by 7σ from these determinations giving rise to the so called proton charge radius puzzle. This variance has led to a very lively discussion in various fields of physics: particle and nuclear physics (proton structure, new physics, scattering analysis), in atomic physics (hydrogen energy level theory, fundamental constants) and fundamental theories (bound-state QED). The origin of this discrepancy is not yet known. The status of the proton charge radius puzzle will be discussed with emphasis on the various ongoing and planned experimental activities which could provide new insight.

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Talks

Proton radius measurements and future prospects M. Mihovilovic The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained (see Fig. 1) and represents a burning problem of today's nuclear physics. Since the observation of the discrepancy in 2010, various explanations for the problem have been offered, ranging from trivial experimental mistakes to those that suggest the need for physics beyond the Standard model. Some of the explanations have already been rejected, while the intriguing ideas, like the introduction of a new mediator particle, still need to be tested. Therefore, several new experiments have been proposed that will provide new constraints to the existing interpretations.

FIG. 1: An overview of the best proton charge radius measurements. Full circles show findings of the scattering experiments. Full squares represent values obtained from the Lamb shift spectroscopy. The values determined from the muonic hydrogen measurements are colored red. The uncertainties of muonic hydrogen data are multiplied by factor 10 for clarity.

High-precision electron scattering experiments are in progress at the Thomas Jefferson National Accelerator Facility and the Mainz Microtron accelerator (MAMI) at the Johannes Gutenberg University Mainz, which are dedicated to investigate the electromagnetic structure of the proton at extremely small four-momentum transfers. As a complement to these measurements, a muon-proton scattering experiment is envisioned at the Paul Scherrer Institute. This will be the first experiment of its kind and will provide information on proton radius from a perspective yet unexplored. Together with the nuclear scattering experiments, new atomic experiments are also foreseen. Very precise Lamb shift measurements in both hydrogen and deuterium are being performed in order to provide further insight into the proton radius puzzle. In this presentation a summary of the existing proton radius measurements will be presented, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. Then, the ongoing and the upcoming experiments dedicated to remeasuring the proton radius will be described. In the last part the preliminary results of the experiment at MAMI will be discussed.

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Talks

Recent results from BESIII Y. Zheng We report an overview of the BESIII recent results on Charmonium decays, light hadron spectroscopy and Charm physics. Some topics on R/QCD studies are also covered. The results are based on the data samples of cms energy between 2 to 4 GeV collected with the BESIII detector at the BEPCII collider.

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49

Talks

Experiment GlueX at Jefferson Lab E. Chudakov The goal of the experiment GlueX is to make a comprehensive search for gluonic excitation in the spectra of light mesons. Recent theoretical developments using Lattice QCD predict hybrid states, including those with exotic quantum numbers, in a mass range accessible using the newly upgraded 12-GeV electron accelerator at Jefferson Lab. Such states, if established, would provide a laboratory for testing QCD in the confinement regime. The experiment is carried out in a new experimental hall at Jefferson Lab (Hall D) and is using a beam of linearly polarized photons produced by the electron beam from the linear accelerator. A new, solenoid-based, hermetic detector is collecting data on meson production and decays. The current status of the GlueX Experiment will be reviewed including the recent developments from the commissioning beam received in Fall 2014 and Spring 2015. The future physics program for Hall D will be outlined.

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Talks

Spectroscopy in the charm region: from BESIII to PANDA

S. Spataro In the last years a renewed interest raised in hadron spectroscopy in the charm sector, triggered by the discovery of new unpredicted states, such as X(3872) and Zc+(3900) at the B factories. Nowadays, the BESIII experiment is accumulating huge data samples of e+e- collisions at a total energy between 2 GeV and 4.6 GeV, to exploit an intensive program of heavy and light hadron spectroscopy, also focused on the study of charmonium-like XYZ states. In spite of the most recent observations, the physics scenario is still not completed and new additional insights will come from the study of antiproton-proton collisions at the FAIR facility, where the Panda spectrometer will operate, at energy up to 5.5 GeV. Panda will provide complementary and unique information on a wide range of hadronic properties, thanks to its peculiar features as compared to e+e- machines: the strong coupling of the annihilation reaction with the gluonic components of the produced hadrons; the possibility to produce resonances with all quantum numbers, including states with spin higher than 2; the possibility to perform energy scans of charmonium and open charm states to precisely determine their widths and line shape. This talk will highlight recent results from BESIII and the prospects for the future Panda experiment.

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51

Talks

Hypernuclear physics at KEK-PS and J-PARC

K. Nakazawa Instead of electron, we located an at-rest − hyperon (dss) in atom, where Ξ− hyperon was produced via (K-, K+) reactions. Ξ− hyperon is captured at higher atomic orbit and cascaded down to lower level with x-ray emission. In usual, the Ξ− hyperon shall feel strong force at the level higher than 3D orbit, which is formed by pure electromagnetic interaction, and then two Λ hyperons (uds) will be produced via strong interaction between the Ξ− hyperon and proton. However, with very little possibilities but a few percent for the reaction, the Ξ− hyperon can be captured at 2p orbit, which is close to the surface of medium-heavy nuclei, such as 12C, 14N and 16O. In this rection, compound nucleus can be formed with double strangeness under the nuclear force, and the nucleus decays associating with daughter nuclei with strangeness. For a quarter century, we have carried out experiments to search for nuclei with double strangeness in nuclear emulsion at KEK-PS, which was already shutdown. The nuclei with two units of strangeness, e.g. double Λ hypernuclei, give information of interaction between two Λ hyperons. Nagara event among nine samples in the world presented Λ-Λ interaction energy to be 0.67 +/- 0.17 MeV, uniquely, and confirmed attractive but weak interaction between two Λ hyperons. This result denied the existence of Λ superfluidity to suppress fast cooling of neutron star. Deeply bound nucleus with Ξ− hyperon, named KISO event, was reported in the case of 14N, recently. Binding energy of the nucleus is 4.38 +/- 0.25 MeV, which is quite larger than the atomic 3D state (0.17 MeV) of the Ξ−14N system. Attractive strong interaction was understood to be worked between Ξ− hyperon and nucleus. Two other events discussed as 3D state capture, were revalued by checking consistency with KISO event. Mass difference between ΛΛ and Ξ−N (N:nucleon) is at most 30 MeV, therefore mixing of them can be occurred, even in neutron star. Experiments shall be started to measure not only A-dependence of ΛΛ interaction but also the level scheme at J-PARC from this autumn as E07, E03 and E05. Thoseexperiments will be introduced with their motivation and expected yield under the present knowledge in this field at the conference, EINN2015.

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Talks

Baryon Spectroscopy: Recent Results and Impact

R. Beck The nucleon excitation scheme has been under intensive investigation with meson photoproduction experiments during the last few years world wide. Currently, a lot of new experimental results are coming out from the CLAS experiment at Jlab, the Crystal Barrel experiment at the ELSA accelerator in Bonn and the Crystal Ball experiment at the MAMI accelerator in Mainz. These experiments focus on the investigation of single and double polarization observables for different meson production reactions using longitudinally and transversely polarized targets, linearly and circularly polarized photon beams as well as the polarization of the recoil protons. The new data sets provide stringent constraints for partial wave analyses of meson photoproduction off the nucleon and will lead to an unique determination of the contributing resonances. The new experimental results will be presented and the impact of the new results to the nucleon excitation spectrum will be discussed.

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53

Talks

Atomic nucleus from QCD on lattice

T. Inoue Explaining and predicting properties of nuclei starting from QCD is one of the most challenging problems in physics. There are several attempts to extract mass of nuclei in lattice QCD simulations, but direct extractions are limited only to very light nuclei, i.e. mass number A≤4, due to computation costs and, more severely, due to several fundamental difficulties. We propose an alternative approach to study nuclei starting from QCD. We deduce mass and structure of 4He, 16O, and 40Ca nuclei from QCD. First, we extract two-nucleon potentials in lattice QCD numerical simulations with the recently developed HAL QCD method, at large quark masses for the moment. Obtained QCD induced NN potentials posses common features of phenomenological ones, namely, strong repulsion at short distance, attraction at medium and long distance, and strong tensor force, although their strength are weaker due to the large quark masses. Accordingly, the potentials reproduce experimental two-nucleon scattering data qualitatively. Then, we apply the potentials to few-body technique or many-body theory to study the nuclei: a variational method for 4He and the Brueckner-Hartree-Fock (BHF) theory for 16O and 40Ca. We find that these nuclei are bound for a large quark mass corresponding to a pseudo-scalar meson mass of 469 MeV and a nucleon mass of 1161 MeV.

Fig. 1 shows obtained ground state energy of 16O as a function of parameters used in our BHF calculation. Fig. 2 shows obtained single particle levels of 40Ca. Total binding energies, 5 MeV for 4He, 35 MeV for 16O, and 113 MeV for 40Ca, are rather smaller than the experimental data, but this is primarily because of the unrealistic quark mass in our lattice QCD simulation. This result shows that one can deduce properties of medium- heavy nuclei from QCD as well as light ones in the HAL QCD approach. This must be significant progress in nuclear physics. References 1. T. Inoue et al. [HAL QCD Collaboration], Nucl. Phys. A881 (2012) 28. 2. T. Inoue et al. [HAL QCD Collaboration], Phys. Rev. Lett. 111 (2013) 11, 112503. 3. T. Inoue et al. [HAL QCD Collaboration], Phys. Rev. C91 (2015) 1, 011001.

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Talks

Electron scattering in Mainz: Plans for the next decade

N. Berger The Mainz Microtron (MAMI) and the associated experiments have long been and continue to be a focusing point for electron and photon scattering studies, ranging from spectroscopy to parity violation experiments. The MAMI program continues at full pace; the Mainz energy recovery superconducting accelerator (MESA), which is currently being developed, will add a second facility for electron scattering physics in Mainz. The first experiment planned is P2, which aims at a determination of the weak mixing angle in parity violating electron-proton scattering at low momentum transfer Q2 with unprecedented precision. The coincidence spectrometer MAGIX will allow for improved proton radius measurements and search for dark photons. Also planned are a beam dump experiment to search for dark matter and an electrostatic storage ring to search for an electron electric dipole moment. The talk will discuss motivation and concepts for the experiments and the current state of R&D.

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55

Posters

Neutron Photo-Pion Amplitudes and Quasi-free Neutral Pion Photoproduction from Deuterium in the Threshold Region H. Stegen, D. Hornidge The isospin characteristics of the neutron and the proton show they are the same particle in different states; however, by analysing the quark content they have an up-down mass difference suggesting a violation in isospin symmetry. This mass difference should have a small effect that can be quantified by the interaction constants know as multipoles. At the Mainzer Microtron (MAMI) an experiment has been conducted in the π0 threshold region in search for the neutron photo-pion amplitudes/multipoles through the d(γ, π0η)p reaction. Electrons were accelerated to 225 MeV and entered the A2 Collaboration hall where they hit a radiator undergoing Bremstrahlung Radiation, producing a photon beam. Photons in the range Eγ = 95.7−208.5 MeV were tagged using the Glasgow-Mainz tagger. The pion-decay photons were measured with the TAPS detector, and a BC-505 liquid scintillator detector measured the energy and angle of the scattered neutron. The proton, with essentially no kinetic energy, enables a quasi-free reaction and allows us to probe an almost free neutron to extract the mulitpoles from the experimental cross sections. Results will be presented.

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Posters

Background Simulations for Experimental Extraction of Neutron Scalar Polarizabilities via Compton Scattering M. Morris, D. Hornidge, J. Annand The A2 collaboration at the Institute for Nuclear Physics in Mainz, Germany, is experimentally determining the polarizabilities of hadrons. The scalar polarizabilities of the neutron, specιfically, have been difficult to determine due to the additional challenges involved. Previous work with deuterium as a target has produced unsatisfactory results due to large uncertainties. Lead by the Glasglow and Mount Allison groups, the A2 collaboration is in the process of preparing a high-pressure, active helium-3 target, which will house events and detect the recoiling nuclei for an experiment set to run in 2016. Recent work using Chiral Perturbation Theory [D.Shulka, A.Nogga, and D. Phillips, NPA 819, 98 (2009)] has shown that coherent Compton scattering on such a target should minimize nuclear effects and allow a more accurate determination of these neutron structure constants. As part of the preparations for the measurement, background studies are being carried out to investigate the contamination that can be expected from the various channels in the Compton data. Preliminary results will be presented.

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Posters The Nuclear Contacts, Photo-Disintegration and Momentum Distributions

R. Weiss, N. Barnea, B. Bazak

A new variable, called the contact, was introduced recently by S. Tan for systems of two component fermions. In our work we generalize the definition of the contact for nuclear systems and use it to study different properties of nuclei, such as short-range correlations and photo nuclear reactions. In ultra cold atomic systems, Tan's contact measures the probability to find two atoms close together and is connected to many properties of the system, such as its energy, pressure and the high momentum tail of the momentum distribution of the atoms. These relations were proved both experimentally and theoretically. The aim of our work is to generalize the definition of the contact to nuclear systems and to use it for finding new and interesting relations between nuclear quantities. So far we have successfully defined the matrices of nuclear contacts and connected them to both the quasi-deuteron (qd) photo-disintegration model and to the high momentum tail of the nucleon momentum distributions. In the generalized definition of the contact, we have taken into consideration all partial waves and finite-range interactions. Regarding the photo-disintegration, we have reformulated Levinger's qd model, resulting a relation between the Levinger constant and the nuclear neutron-proton contacts. For the high momentum tails, we have obtained relations between the contacts and the one-nucleon and the two-nucleon momentum distributions. As a result, we have obtained an asymptotic relation between these two momentum distributions. This relation emphasizes the important contribution of two-body short-range correlations to the high momentum tail and was verified using available Variational Monte Carlo numerical data. Using this numerical data we have also obtained a very good correspondence between our two independent relations (the qd relation and the momentum relations). The numerical data was also used to study more properties of the nuclear contacts, including their scaling along the nuclear chart. The nuclear contacts seem to become a useful tool for studying different properties of nuclear systems. In future works we plan on expanding the contact relations to more aspects of nuclear systems. References: 1. R. Weiss, B. Bazak and N. Barnea, Phys. Rev. Lett. 114, 012501 (2015). 2. R. Weiss, B. Bazak and N. Barnea, arXiv: 1503.07047 [nucl-th] (2015).

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Posters Status of the DarkLight Experiment C. Epstein The DarkLight experiment aims to search for a dark photon with a mass in the range 10-100 MeV/c2. The process e-pe-pe+e- will be studied by using the Jefferson Lab energy-recovering linac's high-intensity 100 MeV, 1 MW electron beam incident on a windowless internal gas hydrogen target. Full track reconstruction of the four-particle _nal state will be performed in order to search for a resonance on the e+-e- invariant mass spectrum. A Phase 1 DarkLight experiment is in preparation that will additionally address new Standard Model measurements at low energy and high intensity, such as radiative MØller scattering. The status of the Phase 1 experiment will be described and the plan for the complete Phase 2 experiment presented.

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Posters Beam tests for the 2015 PANDA Barrel DIRC prototype at CERN

M. Krebs, R. Dzhygadlo, K. Peters, G. Schepers, C. Schwarz, J. Schwiening The PANDA experiment at the Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD. A fast focusing DIRC (Detection of Internally Reflected Cherenkov light) counter will provide hadronic particle identification (PID) in the barrel region of the PANDA detector. The radiator acts also as lightguide, by total internal reflection, preserving the Cherenkov angle. In several beam campaigns different design options for the Barrel DIRC were tested and key components in hard- and software have been optimized. During this summer, the performance of the 2015' prototype was tested in two test beam campaigns in the T9 area at the CERN-PS. The barrel DIRC prototype and auxiliary counters, used as trigger and tracking devices, were positioned in the beamline. Parameters, such as, beam momentum and magnet currents for adjusting the beam focus, were individually adjusted by the user and the prototype's performance was tested over the whole momentum range required in PANDA. The prototype itself was mounted on a remote controlled rotation table. This allowed us to rotate the prototype relative to the beam to perform angular scans from 200 to 1400, representing the barrel region of the PANDA detector system. We obtained the single photon Cherenkov angle resolution of the Barrel DIRC over the whole angular range. In addition different optical components and focusing systems were tested. A narrow bar and a wide plate, both made of quartz glass, were used as radiators and different multi component lenses used as focusing optics. Preliminary results for critical values like photon yield and time resolution will be presented. Furthermore, some performance aspects of the front end electronic boards will be shown. *m.krebs@gsi.de

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Posters The gluon moment from twisted mass lattice QCD

C. Wiese, C. Alexandrou, M. Constantinou, H. Panagopoulos, K. Jansen From experiments it is known that gluons contribute a significant fraction to the nucleon’s total momentum. Nonetheless, there are only a couple of attempts to compute the gluon moment from first principles using lattice QCD. In this work we perform a lattice calculation of the gluon PDF’s first moment <x>g for the nucleon, by the direct computation of nucleon matrix elements of a suitable gluon operator. We employ several steps of stout smearing to the gauge links in the operator in order to improve the signal-to-noise ratio significantly. We present results for two different gauge ensembles: one with Nf = 2+1+1 flavors of maximally twisted mass fermions, on a 323×64 lattice with a pion mass of around 370 MeV, and the other with Nf = 2 flavors of maximally twisted fermions with a clover term, on a 483 × 96 lattice with a physical pion mass. One of the main challenges of this computation is the renormalization pattern which involves mixing with the quark PDF’s first moment, making it difficult to compute it non-perturbatively. To address this issue, we extract the mixing coefficients and the multiplicative renormalization in one-loop perturbation theory, matching the action and smearing parameters to the non-perturbative calculation of the bare gluon moment.

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61

Posters Monte Carlo simulation and event generators for OLYMPUS

J. Bernauer The goal of OLYMPUS is a direct measurement of the two-photon exchange contribution to elastic lepton-proton scattering. A sophisticated simulation of the whole experiment is crucial to extract a precise and correct result. The poster will give an overview of our simulation/analysis framework and describe our implementations of radiative generators for lepton-proton and lepton-lepton scattering.

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Posters Nucleon structure with lattice QCD simulations at physical value of the pion mass A. Abdel-Rehim, C. Alexandrou, M. Constantinou, K. Hadjiyiannakou, K. Jansen, C. Kallidonis, G. Koutsou, A. Vaquero Understanding hadron structure from first principles is considered a milestone of hadronic physics and numerous experiments have been devoted to its study, starting with the measurements of the electromagnetic form factors more than 50 years ago. Lattice QCD (LQCD) is a powerful tool for the ab inition calculation of hadron observables that are either well determined experimentally, or not easily accessible in experiment. Thus, LQCD may provide input to phenomenology as well as new input for beyond the Standard Model Physics. Progress in the simulation of LQCD has been impressive, mainly due to improvements in the algorithms, development of new techniques and increase in computational power, that have enabled simulations to be carried out at parameters very close to their physical values. We present lattice results on the nucleon scalar, axial and tensor charges as well as on the first moments of the unpolarized parton distribution, for both connected and disconnected contributions. Selected results are also given for the electromagnetic form factors and the Dirac and Pauli radii of charge. The computation is carried out using lattice QCD simulations of Nf=2 twisted mass fermions at the physical value of the pion mass. We compare our results with previous twisted mass ensembles and with recent results obtained using different discretization schemes. Finally, we discuss the implications of these results on the spin content of the nucleon.

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Posters Systematic Uncertainties in the OLYMPUS Experiment L. Ice The aim of the OLYMPUS experiment is to determine the multiple photon exchange contribution to elastic lepton-proton scattering. This can be achieved by precisely measuring the positron-proton to electron-proton elastic scattering cross section ratio. OLYMPUS will measure this cross section ratio with an uncertainty of about 1% over a wide range of four-momentum transfer and virtual photon polarization. An accurate ratio measurement requires a complete understanding of the systematic uncertainties. This presentation will discuss some of the systematic uncertainties and the determination of their influence on the ratio measurement.

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Posters The "‘BaBar-Puzzle"’: What remains and why it is important N. Offen, V. Braun, F. Porkert, A. Schäfer Originally the "‘BaBar-Puzzle"’ referred to an unexpected rise at high momentum transfer squared of the γγ* π0 form factor beyond the asymptotic limit. This lead to an increased theoretical activity since the data was difficult to describe in the conventional factorization approach. A later measurement of the γγ* )('η form factor did not show the same behaviour. This again was not easy to reconcile with expectations about the momentum distributions of the quarks inside the respective mesons. The Belle measurement of the pion form factor finally did not show the same rise as the BaBar data but the statistical difference between the two measurements was not very large. We show what remains of the "‘BaBar-Puzzle"’ which points still need clarification and what the most important theoretical issues are in this controversy.

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Posters Hyperon and charmed baryon axial charges from lattice QCD C. Kallidonis, C. Alexandrou, K. Hadjiyiannakou We present results on the axial charges of the two 20---plets of the low---lying baryons from Lattice QCD simulations with dynamical light, strange and charm twisted mass quarks. In addition, we present preliminary results using an ensemble with two degenerate dynamical light quarks with the physical value of the pion mass. While the nucleon axial charge is a well studied quantity both theoretically and experimentally and considered a benchmark calculation within lattice QCD calculations, the axial charge of hyperons and charmed baryons are difficult to extract experimentally. Knowing these quantities for all the baryons is crucial as they provide input to chiral perturbation descriptions. We study the axial charges as a function of the pion mass and perform chiral extrapolations to compare with experimental values wherever available and provide predictions for the rest. Axial charges of the octet and decuplet also allow to check for SU(3) symmetry breaking effects. Moreover, axial charges give information on the intrinsic spin carried by quarks. Assuming that disconnected contributions are small, we show ΔΣq for the nucleon and the other baryons.

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Posters A focusing DIRC detector for GlueX J. Hardin, M. Williams, J. Stevens The GlueX experiment will soon provide unprecedented sensitivity to light-quark exotic meson states. The detector is installed in Hall D at Jefferson Lab, and has begun taking calibration data. A vital upgrade to the particle identification system is currently being developed that makes use of the BaBar DIRC bars. This poster will present the current status of the GlueX focusing DIRC project, including the design and prototyping of a novel focusing system and development of reconstruction algorithms.

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Posters Track reconstruction for the OLYMPUS experiment R. Russell The aim of the OLYMPUS experiment is to precisely measure the ratio of the electron-proton to positron-proton elastic scattering cross sections at a large range of angles for an initial lepton energy of 2 GeV. For each scattering event, the outgoing proton and lepton tracks must be reconstructed in a way that has as little bias with respect to the lepton species as possible. The main OLYMPUS spectrometer consisted of a toroidal magnet with two large drift chamber sectors, on each side of the target, backed by time-of-flight scintillator bars. The data from the 954 drift chamber sense wires and 72 time-of-flight PMTs is combined to reproduce the scattering vertex, angles, and momenta for each track. This process is complicated in the experiment by noise, inefficiencies, position ambiguities, inhomogeneous magnetic field, and the complex time-to-distance functions for each drift chamber sense wire, which must be extracted from data. This presentation will describe how we have tackled this computationally difficult problem in the face of these challenges.

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Posters Model Independent extraction of Multipole Amplitudes from a combined analysis of p(γ,p)π0 and p(γ, π+)n data L. Markou, C. N. Papanicolas, E. Stiliaris, L. Tiator The Athens Model Independent Analysis Scheme (AMIAS) [1, 2] was employed for the simultaneous analysis of p(γ, p)π0 and p(γ, π+)n data. The data include the most recent differential cross section and polarization asymmetries measured at the Mainz Microtron MAMI [3, 4] and an older measurement of the target asymmetry T(γ, π+) from the GWU/SAID database [5]. Following the CGLN formalism [6] which links the multipoles with the photoproduction observables and with all phases constrained by the Fermi-Watson theorem, we extracted all multipole amplitudes that exhibit sensitivity to the data. Adequate partial waves were varied (fitted) so convergence was reached, requiring the inclusion of multipolarities up to l=3. Fixing higher waves to the MAID07 model [7] or by imposing a truncation to the multipole series allowing only partial waves with l ≤ 3 yield agreement and compatibility for the resonant amplitudes and for background amplitudes which indicates convergence and true model independence of the results. The Electric to magnetic ratio reported here EMR(%) = (-2.08 ±0.24) is thus model independent as the simultaneous analysis of data of the γp → pπ0 and γp → nπ+ channels allowed for a full isospin decomposition. Single isospin channel data were also analyzed by freezing all p(1/2) partial waves to MAID07 and extracting only I(3/2) amplitudes, in a more traditional model dependent analysis. The derived results, the correlations among the various amplitudes and the issues of precise estimation of the associated uncertainty in the extracted Multipoles will be presented. [1] C.N. Papanicolas and E. Stiliaris. A novel method of data analysis for hadronic physics. arXiv:1205.6505, (2012) [2] E. Stiliaris and C.N. Papanicolas. Multipole extraction: A novel, model independent method. AIP Conf.Proc.904:257-268,200, (2007) [3] P. Adlarson et al. (A2 Collaboration at MAMI) Measurement of π0 photoproduction on the proton at MAMI C. Phys. Rev. C 92, 024617, (2015) [4] D. Hornidge et al. (A2 Collaboration, CB-TAPS Collaboration) Accurate Test of Chiral Dynamics in the γp→pπ0 Reaction. Phys. Rev. Lett. 111, 062004 , (2013) [5] http://gwdac.phys.gwu.edu/ [6] G.F. Chew, M.L. Goldberger, F.E. Low and Y. Nambu. Application of Dispersion Relations to Low-Energy Meson-Nucleon Scattering. Phys. Rev. 106 (1957) 1337 [7] Drechsel, D., S. S. Kamalov, and L. Tiator. Unitary isobar model –MAID2007. Eur. Phys. J. A34, 69. (2007) http://portal.kph.unimainz.de/MAID//maid2007/ Keywords Monte Carlo Simulation, Model Independent Data Analysis, AMIAS, Hadronic Physics, Multipole Extraction in Nucleon Resonances, Full Isospin Decomposition, EMR

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Posters Future Measurements of the Nucleon Elastic Electromagnetic Form Factors at Jefferson Lab G. Gilfoyle The elastic, electromagnetic form factors are fundamental observables that describe the internal structure of protons, neutrons, and atomic nuclei. Measurements of electron-proton scattering in the 1950's led to the first determination of the proton size and its charge distribution. A half-century later the form factors still lie at the heart of many open questions in nuclear physics. Jefferson Lab in the United States is in the final stages of the 12 GeV Upgrade that will open new opportunities to answer those questions. The electron beam energy has been increased from 6 GeV to 12 GeV, enhancements of the experimental equipment in the three, original end stations (Halls A-C) are complete or nearing completion, and a new end station, Hall D, is online. A campaign to measure all four nucleon form factors (electric and magnetic for both proton and neutron) has been approved consisting of six experiments in Halls A-C. The _rst experiment in Hall A to measure the proton magnetic form factor Gp

M took calibration data at low energy in spring, 2015. These measurements will probe the internal landscape of the nucleon with unequaled precision and range, rigorously test Quantum Chromodynamics (QCD) and other theoretical approaches, and map the transition from the hadronic picture of matter to one based on quarks and gluons. Our current understanding of the form factors varies. The proton magnetic form factor Gp M is measured out to Q2 = 30 GeV2, but the electric one Gp

E is only known to Q2 = 9 GeV2. The neutron form factors (GnM

and Gn

E) are measured less precisely and over a smaller Q2 range; out to 5 GeV2 for GnM and 3:5 GeV2 for Gn

E. On the theory side the grand challenge is to build a QCD-based understanding in the non-perturbative regime where the calculations are daunting. Different approaches (vector meson dominance, constituent quarks, dispersion theory, etc) have been successful in the appropriate range of applicability and give us insight into important aspects of QCD.2 Lattice QCD holds the promise of a fundamental calculation of the form factors. Calculations of the isovector combination of the form factors shows good agreement with the data for pion masses approaching the physical value.2

However, these calculations are still restricted to rather low Q2. The increased beam energy and enhanced end stations at Jefferson Lab will extend the Q2 range. The new Gp

E experiment will reach Q2 = 12 GeV2, GnE will reach ≈ 9 GeV2, and Gn

M will reach ≈13 GeV2. This expansion in Q2 range will be an important challenge to existing theories mentioned above. In this expanded Q2 regime the use of Dyson-Schwinger equations may reveal in detail how the dressed quarks in the nucleon acquire mass and we can use the full set of four, nucleon form factors to extract the flavor dependence of the form factors:3 In this presentation I will expand on the topics described above and present more details on 12 GeV Upgrade. I will include a description of the new accelerator, the suite of detectors in the experimental halls, and the methods used to measure the form factors. 1University of Richmond, Richmond, VA 23173, USA. 2V. Punjabi et al., arXiv:1503.01452 [nucl-ex] and references therein. 3G.D. Cates et al., Phys. Rev. Lett., 106, 252003 (2011).

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Posters Nucleon spin structure functions in chiral perturbation theory F. Hagelstein I will consider the predictions of chiral perturbation theory (XPT) for the spin structure functions g1 and g2 at low Q2 and large x. They will be then used to examine the conflicting XPT predictions [1,2] for the nucleon spin polarizabilities, most notably γ0 and δLT . The novel feature of this work is the comprehensive treatment of the Δ(1232)-contributions, particularly the πΔ-production mechanism shown in the figure.

Figure 1: Graphs contributing to the γN πΔ cross section.

I also shall present a first XPT calculation of the proton polarizability contribution to the 2S hyperfine splitting in muonic hydrogen. The latter results are especially interesting in the context of the proton radius puzzle. References 1. V. Bernard, E. Epelbaum, H. Krebs, U.-G. Meiϐner, Phys. Rev. D 87 (2013) 054032. 2. V. Lensky, J. M. Alarcon, V. Pascalutsa, Phys. Rev. C 90 (2014) 055202.

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Posters Tagged spectator DIS off the deuteron as a tool to extract neutron structure W. Cosyn We present work on a model used to describe the process of tagged spectator DIS off the deuteron. The model uses a factorized approach and includes the effect of final-state interactions at intermediate to large Bjorken x through effective rescattering amplitudes of the produced hadrons X with the "spectator" nucleon. Comparisons with recent Jefferson Lab data are shown and discussed, also for the inclusive DIS case. We discuss the pole extrapolation method applied to the tagged spectator DIS process. This approach is based on the extrapolation of the measured cross sections at different momenta of the detected spectator proton to the non-physical pole of the bound neutron in the deuteron. The advantage of the method is that it makes it possible to suppress nuclear ffects in a maximally model independent way. We apply the method to the recently measured BONuS data to extract the unpolarized neutron structure function at large x, and obtain a surprising x dependence at x≤ 0.6, indicating the possibility of a rise in the neutron to proton structure function ratio. We discuss applications of the method at a possible EIC, both for the unpolarized and polarized case.

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72

Posters Timelike Compton Scattering off the neutron M. Boer Hard exclusive processes such as photoproduction or electroproduction of photon off the nucleon provide access to the Generalized Parton Distributions (GPDs). The GPDs parametrize the complex partonic structure of the nucleon, in a regime where the scattering amplitude can be factorized into a hard calculable part, calculable in QED, and a soft part, depending on the GPDs. GPDs contain the correlation between the longitidunal momentum fraction and the transverse spatial densities of quarks and gluons in the nucleon. Timelike Compton Scattering (TCS) corresponds to the photoproduction of a timelike virtual photon off a nucleon, which subsequently decays into a lepton pair (γN ℓ+ ℓ-N, where ℓ stands for any lepton and N is a nucleon). This process also interferes with the Bethe-Heitler (BH) process, where the incoming photon splits into a lepton pair before the interaction with the nucleon. The BH process has the same final state than the TCS, but doesn't depend on the GPDs. We will present several beam and/or target spin asymmetries for TCS on the neutron and their dependencies on the GPDs. In particular, in the context of the VGG model, we will show the particular sensitivity of some palarization observables to the E GPD and to the angular momentum of the quarks.

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Posters Evaluation of the forward Compton scattering off proton O. Gryniuk, F. Hagelstein, V. Pascalutsa Evaluation of the forward Compton scattering off the proton is done based on Kramers-Kronig kind of relations which express the Compton amplitudes in terms of integrals of photoabsorption cross sections. We evaluate various sum rules using the fits of unpolarized and polarized experimental photoabsorption cross section data. For the sum of proton electric and magnetic dipole polarizabilities, governed by the Baldin sum rule, we obtain the following average (between the two fits): αE1 + βM1 = 14.0(2) Χ 10-4 fm3. An analogous sum rule involving the quadrupole polarizabilities of the proton is evaluated too. We also remark on sum rules for the elastic component of polarizabilities. Both the spin-independent and spin-dependent forward amplitudes of proton Compton scattering are obtained in a broad energy range. The result for spin-independent amplitude is compared with previous evaluations and the only existing experimental data point (at 2.2 GeV). Two nonvanishing observables (di_erential cross section dσ=dΩ and the asymmetry of circularly polarized photons scattered off longitudinally polarized target Σ2z) for the forward Compton scattering off the proton are constructed.

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Posters An Improved Limit for Gamma_ee of X(3872) and Gamma_ee Measurement of psi(3686) M. Ripka Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e+e γISRX(3872) ΓisrΠ+ Π-J/Ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers JPC = 1++ such as the X(3872) via single photon e+e- annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction X(3872)

eeΓ B(X(3872) π+π- J/Ψ ) < 0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the ψ(3686) to be )3686(ψ

eeΓ =2213±18stat ±99sys eV .

Keywords: X(3872), Ψ(3686), Γee, charmonium spectroscopy, BESIII

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75

Posters Two-photon exchange corrections in elastic lepton-proton scattering at small momentum transfer O. Tomalak, M. Vanderhaeghen In recent years, elastic electron-proton scattering experiments, with and without polarized protons, gave strikingly different results for the electric over magnetic proton form factor ratio. A mysterious discrepancy ("the proton radius puzzle") has been observed in the measurement of the proton charge radius in different experiments, one of which is electron-proton scattering. Two-photon exchange (TPE) contributions are the largest source of the hadronic uncertainty. We compare the existing models of the elastic contribution to TPE correction in leptonproton scattering. A subtracted dispersion relation formalism for the TPE in electron-proton scattering has been developed and tested. Its relative effect on the elastic cross section is in the 1- 2 % range for a low value of the momentum transfer. It is shown that the model calculation of the elastic contribution for the proposed muon-proton scattering experiment (MUSE) gives results of the same order as the uncertainty of the planned experiment. The near forward expansion of the inelastic TPE contribution was studied. In sum with theelastic TPE it describes the experimental TPE fit to electron data quite well. In case of the muon scattering (MUSE kinematics) estimates for the inelastic TPE correction are also provided.

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Posters Pion Photoproduction Studies at MAMI P. Martel The A2 tagged photon facility at the Mainzer Microtron (MAMI) has a long history of pion photoproduction experiments. Two of these experiments have recently provided stringent tests of Chiral Perturbation Theory through extraction, via model independent partial wave analysis, of the neutral pion S- and P-wave multipoles near threshold. The first experiment used linearly polarized photons with an unpolarized LH2 target to measure both the beam asymmetry and the unpolarized differential cross section. The second experiment, one of the first in A2 to use the frozen-spin butanol target, provided measurements of polarization dependent cross sections by combining a circularly polarized beam with a transversely polarized target. Having provided the first direct determination of the imaginary part of the E0+ multipole for the proton, the A2 collaboration is planning to both revisit the second of these measurements to reduce the uncertainties and perform a measurement with an active 3He target to extract the E0+ multipole for the neutron, both with the goal of testing isospin breaking. This program of past and future experiments will be presented.

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Posters The Neutron Electric Dipole Moment from lattice QCD C. Alexandrou, A. Athenodorou, M. Constantinou, K. Hadjiyiannakou, K. Jansen, G. Koutsou, K. Ottnad, M. Petschlies We evaluate the neutron electric dipole moment within the framework of lattice QCD. In particular we analyze configurations produced with Nf=2+1+1 twisted mass fermions with light quark mass which corresponds to pion mass of 370 MeV. We do so by extracting the CP-odd form factor F3 at the limit of zero momentum transfer and at small values of the theta-vacuum angle. The zero momentum limit is realized via fitting the momentum dependence by a dipole fit as well as using position space methods. The computation of F3 requires the calculation of the topological charge. We measure the field theoretical topological charge via cooling and gradient flow using the Wilson, Symanzik tree-level improved and Iwasaki actions. Our analysis yields a value for the neutron electric dipole moment of −0.045(6)(1) e·fm in units of theta.

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Posters Dilepton pair production in NA61/SHINE experiment J. Stepaniak, T. Palczewski There are at least two reasons to study the lepton pair production in proton-nucleus and nucleus-nucleus interactions: 1. the dileptons can give access to the early phase of transition from hadronic to quark-gluon form of matter because they pe netrate the hadronic matter without strong interaction, 2. a hypothetical light dark vector boson U could be observed as a narrow peak in the invariant mass of the lepton-antilepton pair (see Ref.1 and references therein). Several experiments (from DLS, HADES, CERES, NA60 to RHIC and LHC) measured the invariant mass distributions of the dileptons but still more systematic studies as a function of incident energy and nucleus size are needed. Moreover some available results are shown in narrow intervals of rapidity. The NA61/SHINE Collaboration studies hadron production in hadron-proton, hadron-nucleus and nucleus-nucleus interactions at CERN Super Proton Synchrotron to perform the energy and system size scan in a search for onset of transition from hadron to quark-gluon matter (Ref.2). During several experiments performed large number of electron-positron pairs has been recorded in addition in the set-up. A substantial fraction of dileptons was produced in the primary vertex. An example of preliminary distribution of the electron-positron invariant mass M(e+e-) from 30 GeV proton-carbon interaction is shown. The momenta and transvers momenta of the e+e- pairs will be presented as well. For comparison, the dielectron invariant mass distribution for external conversion of photons in the detector material shows the narrow maximum in low mass region, as expected from QED calculations. The dilepton pairs from Be-Be and p-Ar as well as from pp interactions at different energies have been collected as well. The analysis is in progress. Upper limits on the U boson coupling to the photon have been set by different experiment for example WASA (from pi0->e+e-gamma decay), KLOE (Phi->eta e+e-) and HADES (inclusive production of e+e- pairs). The limits depends on the U boson mass and there is still need to improve it in some U mass and lifetime regions. 1.R.Essig et al., arXiv:1311.0089 2.NA61 Collaboration (N.Abgrall et al.), JINST 9 (2014) PO 6005, Phys.ReV. C89 (2014) 2,025205

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Posters Search for Tetraquark J^P = 0^+ Candidates by using Lattice QCD A. Abdel-Rehim, C. Alexandrou, J. Berlin, M. Brida, J. Finkenrath, M. Gravina, M. Wagner Within QCD particle states with more then three valence quarks are theoretical possible and several experimental discoveries, like the tetra quark states discovered at BESIII or the possible pentaquark states at LHCb, suggest that the particle structure richer. Here, we will focus on states with four quarks conjectured to be meson-meson states or a diquark–anti-diquark pair such as the light scalar mesons candidates a0(980), f0(980), σ(500), κ(900).

In particular, our search is focusing on JP = 0+ tetraquark candidates with flavor structure q1 q 2q3 q 3

with light quarks q1 and q2 (up- and down) and a heavy quark–anti-quark q3 q 3 (strange or charm). The investigation is done using the Lattice QCD framework. The numerical task is a precise computation of correlation matrices with several different interpolating fields that include two- and four-quarks. This is necessary to quantitatively investigate the internal structure of mesons which are potentially tetraquark states. We will present the status of our study and show some technical details of thecomputation of these diagrams. Moreover numerical results will be discussed for the a0(980) meson.

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80

Posters Hadron multiplicity ratios in semi-inclusive deep-inelastic scattering have been measured on neon, krypton and xenon targets relative to deuterium using the 27.6 GeV beam of HERA at the HERMES experiment. They are presented for pions (π+, π-), kaons (K+, G. Karyan Hadron multiplicity ratios in semi-inclusive deep-inelastic scattering have been measured on neon, krypton and xenon targets relative to deuterium using the 27.6 GeV beam of HERA at the HERMES experiment. They are presented for pions (π+, π-), kaons (K+, K-), protons and anti-protons as a function of the virtual photon energy ν, its virtuality Q2, the fractional hadron energy z and the transverse hadron momentum pt with respect to the direction of the virtual photon. Dependencies are presented in a two-dimensional representation, in the form of detailed binning over one variable and three slices over the other variable. These results may help to understand some aspects of the hadronization process in cold nuclear medium.

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Posters Analysis of e+e−→ nn ̄ from 2015 Scan Data at BESIII S. Ahmed, F. Maas

The analysis of e+e n n cross section at BESIII aims at a measurement of the neutron electromagnetic form factors (EMFFs) in the Time-Like region. The EMFFs are fundamental quantities which parametrize the hadronic current of nucleon, i.e identify its internal structure. The BESIII (Beijing Spectrometer III) at the BEPCII (Beijing Electron Positron Collider II) is one of experiments where measurements of EMFFs can be performed. The effective form factor of the neutron had been measured at FENICE and SND experiments [1,2]. Up to now no separate determination of n

EG and nGM has been done. Therefore, a new data sample has

been collected at BESIII which enables us to separately extract nEG and nGM and hence enables an

accurate determination of nEG and nGM . In this contribution, we will present the current status of

analysis where the dominated background ( e+e- γγ) has been suppressed. The efficiency determination using a data-driven method will be presented as well. References [1] A. Antonelli et al, (FENICE Collaboration), Nucl. Phys. B517, 3 (1998). [2] M. N. Achasov et al, arxiv:1410.3188v1 [hep-ex].