The status of the Excited Baryon Analysis Center

B. Juliá-DíazDepartament d’Estructura i Constituents de la MatèriaUniversitat de Barcelona (Spain)

B. Juliá-Díaz, HADRON 2009, Tallahassee, FSU, 2009

Summary

• Motivation• Model used at EBAC@JLAB• , ,, production:

Hadronic production Photoproduction Electroproduction *

• Expected during 2010

Baryon Resonances

ΔNExciting the substructure we can learn about the forces which keep the quarks together, e.g. using the quark model picture some of the predicted states are:

P11 (939)

L=0, S=1/2, J=1/2+P33 Δ(1232)L=0, S=3/2, J=3/2+

S11 (1535)L=1, S=1/2, J=1/2-

D13 (1520)L=1, S=1/2, J=3/2-

S31 (1620)L=1, S=1/2, J=1/2-

D33 (1700)L=1, S=1/2, J=3/2-

J=1/2 J=3/2 J=3/2 J=1/2

The Δ (1232) and others

• The Delta (1232) resonance stands as a clear peak• The region 1.4 GeV – 2 GeV hosts ~ 20 resonances

N*: 1440, 1520, 1535, 1650, 1675, 1680, ...

Δ : 1600, 1620, 1700, 1750, 1900, …

Δ (1232)100

E.m. probes

• Jefferson LAB (USA)• GRAAL (Grenoble)• MAMI (Mainz)• BATES (MIT)• ELSA (Bonn)• SPring 8 (Japan)

(Courtesy of D. Leinweber)

Originaly, the hope was that probing the structure with electrons would minimize the “hadronic” debris and would give a cleaner access to the properties of nucleons and resonances

Electroproduction of mesons

Main elements:1. Strong-strong interactions2. Hadronic structure of Resonances3. Electromagnetic structure of Resonances

Coupled-channels

EBAC plan and method

EBAC@JLAB

N* propertiesN-N* form factors

Lattice QCDHadron Models

Dynamical Coupled-Channels Analysis @ EBAC

Reaction Data

Formalism (DCC)

Non-resonant + resonant

Dressed resonant vertex

Resonance self energies

Non-resonant amplitude (resummation)

Partial wave amplitude of a b reaction:

Reaction channels:

Potential:

2-body v potential(no N cut) bare N* state2-body Z potential

(with N cut)

EBAC-DCC

A. Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007

5 diagramss-ch Nu-ch Nu-ch Dt-ch rt-ch s

2 diagramss-ch Nu-ch N

3 diagramss-ch Nu-ch Nt-ch

4 diagramss-ch Nu-ch Nt-ch t-ch w

4 diagramss-ch Nu-ch Nu-ch Dt-ch r

1 diagrams-ch N

2 diagramss-ch Nt-ch r

Total 36 diagrams

Two body v’s (strong)

7 diagramss-ch Nu-ch Nu-ch Dt-ch t-ch rt-ch s

contact

4 diagramss-ch Nu-ch Nt-ch r

contact

Total 20 diagrams

5 diagramss-ch Nu-ch Nu-ch Dt-ch

contact

Two body v’s (e.m.)

EBAC framework overview

Physics:Non-resonant obtained from phenomenological LagrangiansUnitarity fulfilled within the modelMost relevant channels included

Up to now , , (s, r, D), near future

Consistent study of all production reactionsCorrect treatment of 3 body cut

TechnicalParallel computing version of the codes needed

Hadronic part(essential starting point)

MBMB (up to 2 GeV)

We introduce explicitly (impose) a minimal number of bare poles, 16 of 23 (4* and 3* from PDG):N: S11(2), P11(2), P13(1), D13(2),

D15(1), F15(1)Δ: S31(1), P31(1), P33(2), D33(1),

F35(1), F37(1)

Technical aspects

Need for extensive parameter search. Several unknowns: e.g. couplings of resonances to MB states

Supercomputing Resources

NERSC LBNL (>500 kh, 07/10) PI: TSH Lee

BSC, Spain (340 kh, 07/08), PI: B. Julia-Diaz

Involved system of coupled integral equations with singularities.

: comparisons to data

EBACSAID06

Data obtained through R. Arndt et al, SAID , gwdac.phys.gwu.eduB. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

ds/d Polarization

: comparisons to data (ii)

: comparing amplitudes• Amplitudes compared to

GWU/SAID amplitudes for the I=1/2 sector

B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

Real part of the AmplitudesImaginary part of the Amplitudes

: comparing TCS • Total Cross sections

compared to experimental data

B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

• Prediction for the total cross sections for each individual channel

: vs other approaches

From M. Paris talk at INT 2009 and R. Arndt talk at Badhonnef 2009

H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) 025206

Not used to constrain the model.

Previous works, mostly tree level:• Meissner et al (1995)• Oset et al (1985)

, distributions

Data handled with the help of R. Arndt

Invariant massdistributions

Phase space

Full model

H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) 025206

Properties of N*(strong)

I. Analytic continuation of T(W) to the unphysical sheet by using contour deformation

II. Poles can be both in the non-resonant and resonant amplitudesIII. One can search for poles of T as a function of W (p’s are arbitrary)

Resonance states

Extraction of Resonances from Meson-Nucleon Reactions.N. Suzuki, T. Sato, T.-S.H. Lee, Phys. Rev. C 79 (2009) 025205; arXiv:0910.1742, part of Suzuki’s PhD Thesis

Resonance Mass

N. Suzuki, B. Julia-Diaz, H. Kamano, A. Matsuyama, TSH Lee, T Sato, arXiv: 0909.1356

Dynamical origin of N(1440)

polesEBAC 1357 - i 76 1364 - i 105

R. A. Arndt et al.(SAID) 1359 - i 82 1388 - i 83

M. Doring et al.(JUELICH) 1387 - i 147/2 1387 - i 71

1. Within our framework the three P11 states evolve from the same bare state.

2. In the fig: evolution of the pole position as we increase the self energy

EBAC current N*

Electromagnetic part

Goal:E.m. meson production

Make use of the vast database for single and double pion photo and electroproduction reactions (JLAB, ELSA, MAMI, …) to:

1) Look for yet unseen resonances2) Confirm the existence of the N*s seen

in the hadronic reactions3) Extract resonance properties:

a) Couplings to meson-baryonb) Electromagnetic structure

Schematic view

Consequence of Unitarity

Data considered:– Differential cross sections

– p 0 p (8793)– p + n (5063)

– Photon asymmetry (Sigma)– p 0 p(1204)– p + n (881)

Consider up to W = 1.6 GeV.

Single pion photoproduction

Analysis performed at specific energies.

B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, L.C. Smith, Phys. Rev. C77, 045205 (2008)

p0p Comparison to data• Total cross section• Differential cross

sections• Target polarization

Single pion photoproduction

Electroproduction

Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, 025207 (2009).

1. Fit1: sT+ sL , sLT , sTT , p(e,e’0)p [Joo et al. PRL02]

2. Fit2 all p(e,e’+)n, p(e,e’0)p3. Fit3 p(e,e’0)p [Joo et al. PRL (2002 & 2003)]

• Consider W<1.65 MeV and Q2<1.45 GeV2

• No assumption on the Q2 dependence of the helicity amplitudes

• Resonances which play a role: S11, P11, P33, D13• Could not fit all the structure functions

simultaneously• Performed several fits to clarify the situation

Data at Q2<1.45 GeV2

Fit1Fit3Fit2

Structure functions (ii)

Q2 = 0.4 GeV2

Solid: Fit1Dashed:Fit2Dotted: Fit3

Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, 025207 (2009).

Coupled channels effects

1. Solid Full Fit12. Dashed only N intermediate (in e.m. piece)3. Data from http://clasweb.jlab.org/physicsdb/

Q2 = 0.4 GeV2

H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv:0909.1129 (2009) (Phys. Rev. C in press)

Study of two pion photoproduction:

• Good description near threshold• Reasonable shape of angular

distributions• Not good description of the total

cross sections of p00 and p+- above 1440 MeV-

Previous (tree level) works include• Meissner (1994)• Gomez Tejedor, Roca,(1993)• Fix et al (2005)

In progress (~ 2010) EBAC second generation model:

Full Combined (global fit) analysis of: N N, N (W<2 GeV) N N (W<2 GeV) N N (W<2 GeV) N N (W<2 GeV) N N (W<2 GeV)

N* structure extraction *N N (W<2 GeV, Q2<4 GeV2) *N N (W<2 GeV) *N N (W<2 GeV)

WEBPAGE: http://ebac-theory.jlab.org

BACKUP

EBAC@JLAB

WEBPAGE: http://ebac-theory.jlab.org

MANPOWER:

Leader (ANL/JLAB):• T.-S.H.Lee

Postdocts (JLAB): • H. Kamano• S. Nakamura• K. Tsushima• A. Sibirtsev

Starting date:• 2006

EXTERNAL COLLABORATORS:

• T. Sato, N. Suzuki (Osaka)• A. Matsuyama (Shizuoka)• B. Julia-Diaz (Barcelona)• B. Saghai, J. Durand (Saclay)

Timeline of EBAC results• Full DCC Formalism

A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rep. (2007)• Hadronic piece fixed (NN, N)(W<2 GeV)

B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2007)J. Durand, B. Julia-Diaz, T.-S.H. Lee, T. Sato, B. Saghai, PRC (2008)

• NN (W<1.6 GeV)B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, LC Smith, PRC (2008)

• NNH. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2008)

• Analytic continuation N. Suzuki, T. Sato, T.-S.H. Lee, PRC (2008)

• *N (W<1.6 GeV, Q2<1.5 GeV2)B. Julia-Diaz, H. Kamano, T.-S.H. Lee, A. Matsuyama, T.Sato, , PRC (2009)

• N (W<1.8 GeV)H. Kamano, B. Julia-Diaz, T.-S.H. Lee, A. Matsuyama, T. Sato, PRC (2010)

Multi step (unitarity) How do we produce

meson-baryon states?

• Directly• Through MB states• Through MMB states

• We need to incorporate all

the possibilities Unitarity Coupled-channels

σTOT (b)

Structure functions

Q2 = 1.45 GeV2

Solid: Fit1

H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv:0909.1129 (2009), Phys. Rev. C in press

, N* effects

PDG *s and N*’s origin

Are they all genuine quark/gluon excitations?

|N*> =| qqq >

Is their origin dynamical? E.g. some could be understood

as arising from meson-baryon dynamics

|N*>= | MB >

Most of their properties are extracted from

N N N N

Z terms

The status of the Excited Baryon Analysis Center

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