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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
3H. Avakian, LNF, Mar 18
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
H. Avakian, LNF, Mar 184
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
H. Avakian, LNF, Mar 18
Large acceptance detectors would allow simultaneous measurements in full xF-range, including target and current regions of SIDIS and exclusive
processes.
H. Avakian, LNF, Mar 1866
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%
H. Avakian, LNF, Mar 18
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.
H. Avakian, LNF, Mar 18
Musch et al, arXiv:1011.1213
CLAS/HERMES
Force on the active quark right after scattering (Burkardt)
Sergio Anefalos-Pereira
H. Avakian, LNF, Mar 189
Dihadron asymmetries from CLAS
SIDIS (TMDs)
DVMP (GPDs)
Dihadron double spin asymmetry measured at 6 GeV consistent with DIS
CLAS Preliminary
S. Anefalos Pereira
H. Avakian, LNF, Mar 1810
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
H. Avakian, LNF, Mar 1811
Accessing transversity in dihadron production at JLab Measurements with polarized protons Measurements with polarized neutrons
CLAS12 SoLID
H. Avakian, LNF, Mar 1812
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.
H. Avakian, LNF, Mar 1813
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
H. Avakian, LNF, Mar 1814
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
H. Avakian, LNF, Mar 1815
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
16H. Avakian, LNF, Mar 18
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
17H. Avakian, LNF, Mar 18
•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
H. Avakian, LNF, Mar 18
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
H. Avakian, LNF, Mar 1819
~
Unpolarized beam, longitudinal target (TSA) :
UL ~ sinIm{F1H +(F1+F2)(H + xB/2E) –kF2 E+…}d~
Im{Hp, Hp}~
GK-GL-
H. Avakian, LNF, Mar 1820
•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
H. Avakian, LNF, Mar 1821
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)
H. Avakian, LNF, Mar 1822
K+ separation
Detection of K+ p and - would allow to separate of different final states (,K*)
q
K+
Analysis framework
• Differential input (SIDIS):
H. Avakian, LNF, Mar 1823
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)
H. Avakian, LNF, Mar 1824
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.
H. Avakian, LNF, Mar 1825
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
H. Avakian, LNF, Mar 1826
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
28H. Avakian, LNF, Mar 18
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
H. Avakian, LNF, Mar 1829
Exclusive kaon production
H. Avakian, LNF, Mar 1830
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
H. Avakian, LNF, Mar 1831
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
H. Avakian, LNF, Mar 1832
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
H. Avakian, LNF, Mar 18
H. Avakian, LNF, Mar 1834
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!!!)
35H. Avakian, LNF, Mar 18
F. Aaron et al., JHEP 1001 (2010) P. Jimenez-Delgado et al (2014), 1403.3355.
H. Avakian, LNF, Mar 1836
Exclusive separation
Detection of the complete final sate allow separation of exclusive s
Correlations between target and current
H. Avakian, LNF, Mar 1837
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.
H. Avakian, LNF, Mar 1838