Studies of spin-orbit correlations at JLab Harut Avakian (JLab) 1 H. Avakian, LNF, Mar 18 LNF SIDIS...

Studies of spin-orbit correlations at JLab

Harut Avakian (JLab)Harut Avakian (JLab)

1H. Avakian, LNF, Mar 18

LNF SIDIS working group meeting Frascati March 18

H. Avakian, LNF, Mar 182

QCD: from testing to understanding

Testing stage: pQCD predictions, observables in the kinematics where theory predictions are easier to get (higher energies, 1D picture, leading twist, current fragmentation, IMF)

Understanding stage: non-perturbative QCD, strong interactions, observables in the kinematics where most of the data is available (all energies, quark-gluon correlations, orbital motion)

nucleon in 3D

quark-gluon correlations

spin-orbit correlations

evolution,factorization

hadronizationparton

distributions

strong interactions

&quark gluon dynamics

spectroscopy,excited states

0h DIS

1h SIDIS/DVMP

2h SIDIS/DVMP

production in SIDIS provides access to correlations inaccessible in simple SIDIS

target fragmentationentanglement

Hadron production in hard scattering

xF - momentum

in the CM frame

xF>0 (current fragmentation)

xF<0 (target fragmentation)

h

L

LKarliner, Kharzeev , Ellis & KotzinianStrikman,Weiss & SchweitzerAnselmino, Barone, Kotzinian

X. Artru & Z. Belghobsi

Correlations of the spin of the target or/and the momentum and the spin of quarks, combined with final state interactions define the azimuthal distributions of produced particles

FSI


Features of partonic 3D non-perturbative distributions

• transverse position and momentum of partons are correlated with the spin orientations of the parent hadron and the spin of the parton itself

• transverse position and momentum of partons depend on their flavor

• transverse position and momentum of partons are correlated with their longitudinal momentum


Understanding of the 3D structure of nucleon requires studies of spin and flavor dependence of quark transverse momentum and space distributions

Need a new MC generator “PYTHIA with spin-orbit correlations” to simulate azimuthal and spin correlations in final state hadronic distributions.

• spin and momentum of struck quarks are correlated with remnant

• quark-gluon interaction play a crucial role in kinematical distributions of final state hadrons, both in semi-inclusive and exclusive processes

L

55

h

Leading Twist Generalized PDFs

Target fragmentation Current fragmentation

Fracture Functions

xF

M

0-1 1

hh

PDF GPD

kT-dependent PDFs Generalized PDFs

FFDA DA

exclusivesemi-inclusive


Large acceptance detectors would allow simultaneous measurements in full xF-range, including target and current regions of SIDIS and exclusive

processes.


Quark distributions at large kQuark distributions at large kTT: lattice: lattice

B.Musch et al arXiv:1011.1213

B.Pasquini et al

Distributions of PDFs may depend on flavor and spin (lower fraction aligned with proton spin, and less u-quarks at large kT,bT)

g1q=q=(q+-q-)/2

arXiv:0705.4345

G. Miller et al (2011 )

7

JLab Experimental Halls

Polarized target

IC

Hall B

424 PbWO4

~87% ~8% ~1.5%


8

Quark-gluon correlations: Models vs Lattice

• Models agree on a large e/f1 -> large beam SSA • Lattice results for u-d can be directly compared to models and data.


Musch et al, arXiv:1011.1213

CLAS/HERMES

Force on the active quark right after scattering (Burkardt)

Sergio Anefalos-Pereira


Dihadron asymmetries from CLAS

SIDIS (TMDs)

DVMP (GPDs)

Dihadron double spin asymmetry measured at 6 GeV consistent with DIS

CLAS Preliminary

S. Anefalos Pereira


Dihadron production at JLAB12 Use the clasDIS (LUND based) generator + FASTMC

to study pairs xF - momentum

in the CM frame

Dihadron sample defined by SIDIS cuts+xF>0 (CFR) for both hadrons

Wide angular coverage is important

SoLIDCLAS12


Accessing transversity in dihadron production at JLab Measurements with polarized protons Measurements with polarized neutrons

CLAS12 SoLID


Aybat, Prokudin & Rogers C12-11-111

• Large acceptance of CLAS12 allows studies of PT and Q2-dependence of SSAs in a wide kinematic range• Comparison of JLab12 data with HERMES, COMPASS (and

EIC) will pin down the non-trivial Q2 evolution of Sivers asymmetry.


Sivers effect in the target fragmentation

Wide coverage of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region

arXiv:1502.02669

P2

P1


Accessing Sivers TMD in dihadron production at JLab

•Measurements with polarized protons @ CLAS12•Measurements with polarized neutrons @SOLID•Measurements with EIC

A. Kotzinian, H. H. Matevosyan, and A. W. Thomas,Phys.Rev.Lett. 113, 062003 (2014), 1403.5562.

After integration over the azimuthal angle of total transverse momentumThe asymmetry as a function of the relative transverse momentum

1st harmonic of the cos(T-R)

R≠0 can be ensured, by choosing asymmetric cuts on the minimum values of z1 and z2.

arXiv:1502.02669

Proposal for PAC43


Back-to-back hadron (b2b) production in SIDIS

The beam–spin asymmetry appears, at leading twist and low transverse momenta, in the deep inelastic inclusive lepto-production of two hadrons, one in the target fragmentation region and one in the current fragmentation region.

M. Anselmino, V. Barone and A. Kotzinian, Physics Letters B 713 (2012)

Back-to-back hadron production in SIDIS would allow: •study SSAs not accessible in SIDIS at leading twist•measure fracture functions•control the flavor content of the final state hadron in current fragmentation (detecting the target hadron)•study correlations in target vs current and access factorization breaking effects (similar to pp case)•access quark short-range correlations and SB (Schweitzer et al)•...

P2

P1

Silvia Pisano

Target fragmentation region: production

polarization tranfer coefficient

60 days of CLAS12


probability to produce the hadron h when a quark q is struck in a proton target

Measurements of fracture functions opens a new in studies of the structure of the nucleon in general and correlations between current and target fragmentation in particular

•Large acceptance of CLAS12 and EIC provide a unique possibility to study the nucleon structure in target fragmentation region and correlations of target and current fragmentation regions

Jeff Phillips

Controlling the flavor content with target-current correlations


•Large acceptance of CLAS12 (and EIC) provide a unique possibility to detect simultaneously hadrons in the forward and backward regions

e e’

pπ

X

K

xF

18

3D structure: GPDs


Spin-azimuthal asymmetries in hard exclusive production of photons and pions give access to underlying GPDs

Transverse photon dominates the x-section for exclusive 0 production

epe’p

CLAS e1dvcs

Lattice (QCDSF)

DVCS asymmetries measured at HERMES & JLABMore measurements atJLab, Compass

t-dependence of H


~

Unpolarized beam, longitudinal target (TSA) :

UL ~ sinIm{F1H +(F1+F2)(H + xB/2E) –kF2 E+…}d~

Im{Hp, Hp}~

GK-GL-


•CLAS12 can measure Q2 dependence of HT SSAs significantly extending the range of CLAS

Goldstein, Liuti et alP.Kroll & S. Goloskokov

•The production amplitude at large Q2 factorizes into the hard subprocess and GPDs •Within the handbag approach*T transitions are related to transversity (helicity-flip) GPDs accompanied by a twist-3 pion wave function

Hard partonic subprocess

t-dependences of HT epe’p

predictions (GK)

from the upolarizeddata (CLAS)

polarized data (Kim)

SSAs in exclusive kaon production


Kasymmetries are predicted to be large and with opposite sign to K

Goloskokov&Kroll

Goldstein, Hernandez, & Liuti

Exclusive production of K and Kprovide access to different combinations of chiral-odd GPDs

Beam and target asymmetries in exclusive production of K and Kare very sensitive to chiral-odd GPDs.

Proposal for PAC43 (A.Kim et al)


K+ separation

Detection of K+ p and - would allow to separate of different final states (,K*)

q

K+

Analysis framework

• Differential input (SIDIS):


bin# x Q2 y W MX z PT N(counts) RC

1...N

bin# x Q2 y W MX t N(counts) RC

1...N

The size of the bins will be defined by the TMD/GPD extraction framework

• Differential input (DVMP):

M. Aghasyan et al arXiv:1409.0487 (JHEP)


Summary

The main goal of the upgraded JLab 3D program is the study of spin and flavor dependence of transverse space and transverse momentum distributions of quarks.

•Understanding of target fragmentation and correlations between hadrons in target and current fragmentation regions is important for interpretation of semi-inclusive and exclusive production of hadrons.

•Identification of Kaons will significantly enhance CLAS12 capabilities to study flavor dependence of transverse distributions in semi-inclusive and exclusive processes.

•Measurements with unpolarized, longitudinally and transversely polarized targets of hard exclusive and semi-inclusive processes will help to accomplish the CLAS12 program of studies of the 3D structure of the nucleon.Need TMD/CFF extraction framework with controlled systematics.


Support slides….

0 0.5 1.0

P.Schweitzer et al. arXiv:1210.1267

Higher probability to find more sea quarks at large kT

• Predictions from dynamical model of chiral symmetry breaking [Schweitzer, Strikman, Weiss JHEP 1301 (2013) 163]

-- kT (sea) >> kT (valence) -- short-range correlations between partons (small-size q-qbar pairs) -- directly observable in PT-dependence of hadrons in SIDIS

Dynamical mechanisms creating nucleon sea?

Non-perturbative sea in nucleon due to chiral symmetry breaking

-- Large flavor asymmetry dbar > ubar as evidence -- Partonic expression of q-qbar vacuum condensate?

-- Related to dynamical mass generation –

COMPASS Preliminaryh+ from D

Mh (

arb

itra

ry u

nit

s)

0.30 < z < 0.6<x> = 0.054 <Q2>=4.57


Exclusive +/ arXiv:0906.0460

Different transverse moments will give access to different combinations of GPDsH. Avakian, LNF, Mar 18

27

Flavor separation of form factors

G. Cates et al. PRL 106 (2011) 252003

Q4 F

2q/

Q4 F

1q


G. Miller et al (2011 )

space distributions depend on flavor and spin (modify in medium)

Quark transverse charge densities inside an unpolarized proton arXiv:1304.5926

• form factors of the nucleon fell off faster in nuclear matter

http://arXiv.org/abs/arXiv:1304.5926

Exclusive kaon production


Exclusive production of K and Kprovide access to different combinations of chiral-odd GPDs

Unlike + the K+ x-section is totally dominated by the transverse photon

pole contribution negligible


Transverse momentum dependence of sea quark distributions

Understanding of the 3D structure of nucleon requires studies of spin and flavor dependence of quark transverse momentum distributions

TMD PDF for a given combination of parton and nucleon spins

To apply the TMD formalism to data we need to understand the basic properties of the TMDs at a low scale, determined by non-perturbative QCD interactions

Dynamical mechanisms producing intrinsic transverse momentum in the nucleon may be be very different for valence and sea quarks

• kT-distributions of valence quarks governed by the overall size of the nucleon of ~1fm (bag,light-front,..)

• sea kT~vacuum fluctuations (0.3 fm), with significant contribution from short-range forces (ex. flavor structure of the sea)

Nucleon could be regarded as a many-body system with short-range correlations induced by the chiral-symmetry breaking interactions.

NuSea, Phys.Rev. D64 (2001) 052002

Exclusive 0

T – dominates for 0.

dT /dt

dL /dt

rates higher for small W

M 0+,++ amplitude is important in T .

K2⊥/Q2 corrections in the propagators of the hard

subprocess amplitude are essential in the description of the cross section at low Q2. They decrease by a factor of about 10 at Q2 3GeV∼ 2


33

Evolution Studies: from JLab12 to EIC

•Q2 – dependence of Sivers function is sensitive to the non-perturbative physics•Wide range in Q2 is crucial to study the evolution•Study of large x domain requires high luminosity •Overlap of EIC and JLab12 in the valence region will be crucial for the TMD program

JLab@12GeV (25/50/75)0.1<xB<0.7 : valence quarksEIC √s = 140, 50, 15 GeV 10-4<xB<0.3: gluons and quarks, higher PT and Q2.

Aybat,Prokudin&Rogers hep:1112.4423Sun & Yuan arXiv:1304.5037

JLab12

EIC@Jlab/BNL

EIC@HIAFENC@FAIR

Q2



K/K* and separation

Due to detector resolution clean separation of different channels (,K*) will require detection of 4 particles

Studies of 1D PDFs

• Strong model and parametrization dependence observed already for 1D PDFs• Positivity requirement may change significantly the PDF (need self consistent fits of

polarized and unpolarized target data!!!)


F. Aaron et al., JHEP 1001 (2010) P. Jimenez-Delgado et al (2014), 1403.3355.


Exclusive separation

Detection of the complete final sate allow separation of exclusive s

Correlations between target and current


L

•how the remnant system dresses itself up to become a full-fledged hadron•correlation with the spin of the target or/and the produced particles

The sum rule including the OAMJi’s quark and gluon kinetic angular momentum can be expressed in terms of twist-2 GPDs.

the z-component of the quark kinetic OAM is related to a pure twist-3 GPD (Polyakov et al)

C.Lorce, B. Pasquini arXiv:1208.3065

describes the vector distribution of quarks inside a longitudinally polarized target ->related to the z -component of angular momentum.


Studies of spin-orbit correlations at JLab Harut Avakian (JLab) 1 H. Avakian, LNF, Mar 18 LNF SIDIS...

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