TMD measurements at CLAS. Harut Avakian (JLab). 3rd Workshop on the QCD Structure of the Nucleon (QCDN'12) October 2226, 2012 Bilbao, Spain. Outline. Transverse structure of the nucleon and partonic correlations. Introduction
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Harut Avakian (JLab)
3rd Workshop on the QCD Structure of the Nucleon (QCDN'12) October 2226, 2012Bilbao, Spain
H. Avakian, QCDN'12, Oct 23
Transverse structure of the nucleon and partonic correlations
Introduction
Hard scattering processes and correlations between spin and transverse degrees of freedom
kTeffects with polarized SIDIS
Higher twist effects in SIDIS
Summary
H. Avakian, QCDN'12, Oct 23
SemiInclusive processes and transverse momentum distributions
/
PDFs, q(x): Probabilities to find a quark with a fraction x of proton momentum P
h
TMD
Hard exclusive processes and spatial distributions of partons
B.Pasquini et al
g,h
Detection of final state particles in semiinclusive and hard exclusive processes allows access also to transverse distribution of quarks.
GPD
arXiv: 1106.6177
Collinear analysis of observables in semiinclusive and hard exclusive processes will be sensitive to integration region over transverse degrees of freedom due to correlations of x, spin and transverse degrees of freedom.
Collinear analysis of observables in semiinclusive and hard exclusive processes will be sensitive to integration region over transverse degrees of freedom due to correlations of x, spin and transverse degrees of freedom.
H. Avakian, QCDN'12, Oct 23
kT
p┴
PT = p┴+zkT
Transverse momentum of hadrons in SIDIS provides access to orbital motion of quarks
H. Avakian, QCDN'12, Oct 23
quark polarization
Higher Twist PDFs
Experiment for a given target polarization measures all moments simultaneously
5
H. Avakian, QCDN'12, Oct 23
q
Dq
MR, R=s,a
JMR model
B.Musch et al arXiv:1011.1213
Higher probability to find a quark antialigned with proton spin at large kT
g1q=Dq=(q+q)/2
Higher probability to find a dquark with at large kT
kTdistributions of TMDs may depend on flavor and spin
6
H. Avakian, QCDN'12, Oct 23
ep→e’pX
Inner Calorimeter
(DVCS experiments)
e
p
p+
Unpolarized and longitudinally polarized targets
Unpolarized, longitudinally and transversely polarized targets
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H. Avakian, QCDN'12, Oct 23
A1 – PT dependence
H. A. & CLAS Coll., PRL.105:262002, 2010
m02=0.25GeV2
mD2=0.2GeV2
M. Anselmino et al PRD74:074015, 2006
0.4<z<0.7
S. Skoirala
CLAS PRELIMINARY
B.Musch et al arXiv:1011.1213
p+ A1 suggests broader kT distributions for f1 than for g1
The new data is consistent with old measurements, now available in several bins in x
H. Avakian, QCDN'12, Oct 23
HERMES
CLAS (5days)
S. Skoirala
CLAS PRELIMINARY
B.Musch arXiv:0907.2381
Worm gear TMDs are unique (no analog in GPDs)
H. Avakian, QCDN'12, Oct 23
hepex/0104005
Kotzinian et al (1999)
S. Skoirala
CLAS PRELIMINARY
CLAS PRELIMINARY
The sinfmoments of p0and p+of target SSA comparable, while
p SSA seem to have an opposite to p0/+ sign at CLAS (also HERMES)
H. Avakian, QCDN'12, Oct 23
Longitudinally Polarized Beam SSA
HT function related to force on the quark. Burkardt (2008),Qiu(2011)
ALUCLAS @4.3 GeV (2003)
Efremov et al (2003)
W. Gohn
M.Aghasyan
W. Mao, Z. Lu (arXiv:1210.4790)
CLAS e1dvcs
CLAS 5.5 GeV
x vs kT correlations matter
Collins type contribution may be dominant for p
Sivers type contribution may be dominant for p0
H. Avakian, QCDN'12, Oct 23
Lattice provides important cross check with data and models for all HT TMDs (Musch et al, arXiv:1011.1213)
H. Avakian, QCDN'12, Oct 23
h1
h2
Dihadron production kinematics
 fractions of energy carried by a hadrons
Dihadron productions offers exciting possibility to access HT pdfs as we deal with the product of functions instead of convolution
H. Avakian, QCDN'12, Oct 23
Dihadron production kinematics
Data vs MC
S. Anefalos Pereira
Dihadron productions offers exciting possibility to access HT parton distribution surviving kTintegration
H. Avakian, QCDN'12, Oct 23
epe’pg
epe’pp0
CLAS e1dvcs
CLAS eg1dvcs
CLAS eg1
HERMES
Liuti&Goldstein
Kroll&Goloskokov
Q2 (GeV2)
Eim vs t
CLAS eg1dvcs
VGG
PR1212010
xB
xB
Spinazimuthal asymmetries in hard exclusive photon (DVCS) and hadron (DVMP) production give access to underlying GPDs and PDFs
H. Avakian, QCDN'12, Oct 23
Jlab measurements at 6 GeV provide important input for model independent flavor decomposition of TMDs and GPDs
tools are required to extract the 3D PDFs in multidimensional space
H. Avakian, QCDN'12, Oct 23
H. Avakian, QCDN'12, Oct 23
M. Aghasyan, K. Allada, H. Avakian, F. Benmokhtar, E. Cisbani, JP. Chen, M. Contalbrigo, D. Dutta, R. Ent, D. Gaskell, H. Gao, K. Griffioen, K. Hafidi, J. Huang, X. Jiang, K. Joo, N. Kalantarians, ZE. Meziani, M. Mirazita, H. Mkrtchyan, L.L. Pappalardo, A. Prokudin, A. Puckett, P. Rossi, X. Qian, Y. Qiang, B. Wojtsekhowski
for the Jlab SIDIS working group
H. Avakian, QCDN'12, Oct 23
(PDFs in terms of Lorenz invariant amplitudes
Musch et al, arXiv:1011.1213)
c2
s2
H. Avakian, QCDN'12, Oct 23
SSAs in exclusive pion production
CLAS Preliminary
Ahmad,Liuti & Goldstein: arXiv:0805.3568
Gloskokov & Kroll : arXiv:0906.0460
Transverse photon matters
HERMES
H. Avakian, QCDN'12, Oct 23
Exclusive p0 production
H. Avakian, QCDN'12, Oct 23
Sivers TMD evolution
DrellYan
SIDIS
Aybat, Prokudin & Rogers
C1211111
TMD Evolution may explain existing differences between HERMES and COMPASS .
Aybat, Prokudin & Rogers : arXiv:1112.4423
Comparison of JLab12 data with HERMES and COMPASS will pin down the Q2 evolution of Sivers asymmetry.
H. Avakian, QCDN'12, Oct 23
arXiv:1003.4549
A1
PT
B.Musch et al arXiv:1011.1213
CLAS data consistent with model predictions and lattice predicting that width of g1 is less than the width of f1
H. Avakian, QCDN'12, Oct 23
Q2
EIC
JLab12
From JLab12 to EIC
Aybat,Prokudin&Rogers arXiv:1112.4423
H. Avakian, QCDN'12, Oct 23
ep→e’p+X
JLAB 50 GeV
JLAB 50 GeV
For a given lumi (30min of runtime) and given bin in hadron z and PT, higher energy provides higher counts and wider coverage in Q2, allowing studies of Q2 evolution of 3D partonic distributions in a wide Q2 range.
H. Avakian, QCDN'12, Oct 23
l
l’
BHS 2002
Collins 2002
Ji,Yuan 2002
x,kT
spectator system
proton
soft gluon exchanges included in the distribution function (gauge link)
H. Avakian, QCDN'12, Oct 23
Forces and binding effects in the partonic medium
Interaction dependent parts
“WandzuraWilczek approximation” is equivalent to setting
functions with a tilde to zero.
Quark polarized in the xdirection with kT in the ydirection
BoerMulders Force on the active quark right after scattering (t=0)
Interpreting HT (quarkgluonquark correlations) as force on the quarks (Burkardt hepph:0810.3589)
28
H. Avakian, QCDN'12, Oct 23
Directly obtained ETQS functions are opposite in sign to those from kT moments “sign mismatch”
Sivers function extracted assuming kT distribution is gaussian
(Z. Kang et al, 2011)
H. Avakian, QCDN'12, Oct 23
Q2dependence of beam SSA
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist3)
1/Qbehavior expected (fixed x bin)
Study for Q2 dependence of beam SSA allows to check the higher twist nature and access quarkgluon correlations.
H. Avakian, QCDN'12, Oct 23
H. Mkrtchyan(DIS2011)
xdependence of p+/p ratio is good agreement with the quark parton model predictions (lines CTEQ5M+BKK).
H. Avakian, QCDN'12, Oct 23
Perturbative limit calculations available for :
J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238
M.Anselmino et al hepph/0608048
m02=0.25GeV2
mD2=0.2GeV2
32
H. Avakian, QCDN'12, Oct 23
q
Dq
JMR model
MR, R=s,a
B.Musch et al arXiv:1011.1213
Du/u
Sign change of Du/u consistent between lattice and diquark model
33
H. Avakian, QCDN'12, Oct 23
PTdependence of beam SSA
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist3)
In the perturbative limit 1/PT behavior expected
Perturbative region
Nonperturbative TMD
Study for SSA transition from nonperturbative to perturbative regime. EIC will significantly increase the PT range.
H. Avakian, QCDN'12, Oct 23
SIDIS MC in 8D (x,y,z,f,fS,pT,l,p)
Simple model with 10% difference between f1 (0.2GeV2) and g1 widths with a fixed width for D1 (0.14GeV2)
CLAS12 acceptance & resolutions
p┴
Events in CLAS12
PT = p┴+zkT
LundMC
Reasonable agreement of kinematic distributions with realistic LUND simulation
H. Avakian, QCDN'12, Oct 23
ep→e’p+X
24 GeV
50 GeV
For a given lumi (30min of runtime with L=1035cm2s1 ) and given bin in hadron z and PT, higher energy provides higher counts and wider coverage in x and Q2
H. Avakian, QCDN'12, Oct 23
p
5GeV
50 GeV

BoerMulders Asymmetry with CLAS12 & EICTransversely polarized quarks in the unpolarized nucleon
CLAS12
sin(fC) =cos(2fh)
EIC
Perturbative limit calculations available for :
J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238
Nonperturbative TMD
Perturbative region
CLAS12 and ELICstudies of transition from nonperturbative to perturbative regime will provide complementary info on spinorbit correlations and test unified theory (Ji et al)
H. Avakian, QCDN'12, Oct 23
Sivers effect: Kaon electroproduction
EIC
CLAS12
H. Avakian, QCDN'12, Oct 23
hp mmX
ee ppX
BOERMULDERS
Spin Orbit effect
E615
NA10
E866
TMD Correlation Functions in other experiments
Fragmentation Functions (FF)
COLLINS
Quark spin probe
In dihadron case Interference Fragmentation Function (IFF)
H. Avakian, QCDN'12, Oct 23
Pretzelosity @ EIC
5x50 epX
p
p+
H. Avakian, QCDN'12, Oct 23
ep→e’p+X
Wider x range allow studies of transverse distributions of sea quarks and gluons
Wider PT range will be important in extraction of kTdependences of PDFs
For a given lumi (30min of runtime with 1035) and given bin in hadron z and PT, higher energy provides higher counts and wider coverage in x and PT to allow studies of correlations between longitudinal and transverse degrees of freedom
H. Avakian, QCDN'12, Oct 23
ep→e’p+X
For a given lumi (30min of runtime) and given bin in hadron z and PT, higher energy provides higher counts and wider coverage in Q2, allowing studies of Q2 evolution of 3D partonic distributions in a wide Q2 range.
H. Avakian, QCDN'12, Oct 23
H. Avakian, QCDN'12, Oct 23
kicked in the opposite to the leading pion(into the page)
L
Subleading pion opposite to leading (double kick into the page)
Simple string fragmentation (Artru model)
p+
Leading pion out of page (  direction )
z
L
p
If unfavored Collins fragmentation dominates measured p vs p+, why K vs K+ is different?
45
45
H. Avakian, QCDN'12, Oct 23
Pasquini and Yuan, Phys.Rev.D81:114013,2010
H. Avakian, QCDN'12, Oct 23
A1 – PT dependence
H. Avakian & CLAS Coll., PRL.105:262002, 2010
0.4<z<0.7
M. Anselmino et al PRD74:074015, 2006
m02=0.25GeV2
mD2=0.2GeV2
p+ A1 suggests broader kT distributions for f1 than for g1
p A1 may require nonGaussian kTdependence for different helicities and/or flavors
H. Avakian, QCDN'12, Oct 23
Compare single hadron and dihadron SSAs
Only 2 terms with common unknown HT G~ term!
HTdistributions and dihadron SIDISM.Radici
Projections for (p+K) (K+p) for 580 fb1
Aurore Courtoy/Anselm Voosen  Spin session
H. Avakian, QCDN'12, Oct 23
Transverse momentum distributions in hadronization may be flavor dependent
=>measurements of different final state hadrons required
NJL model H. Matevosyan et al. arXiv:1011.1052 [hepph]
proton
H. Avakian, QCDN'12, Oct 23
need
Combined analysis of Collins fragmentation asymmetries from proton and deuteron and for p and K may provide independent to e+e (BELLE/BABAR) information on the underlying Collins function.
H. Avakian, QCDN'12, Oct 23
Compare single hadron and dihadron SSAs
fh
y
Only 2 terms with common unknown HT G~ term!
PT
fS=p
x
Chiral odd HTdistributionHow can we separate the HT contributions?
HT function related to force on the quark. M.Burkardt (2008)
M.Radici
H. Avakian, QCDN'12, Oct 23
Large PT may have significant nuclear contribution
52
52
H. Avakian, QCDN'12, Oct 23
quark polarization
53
H. Avakian, QCDN'12, Oct 23
JLab, Nov 25
quark polarization
54
H. Avakian, QCDN'12, Oct 23
JLab, Nov 25
Twist3 PDFs : “new testament”
H. Avakian, QCDN'12, Oct 23
TMD PDFs
H. Avakian, QCDN'12, Oct 23
p+
leading pion out of page
Simple string fragmentation for pions (Artru model)
z
L
r production may produce an opposite sign AUT
Leading r opposite to leading p(into page)
z
r
L
Fraction of direct kaons may be significantly higher than the fraction of direct pions.
LUNDMC
H. Avakian, QCDN'12, Oct 23
A.Kotzinian
High statistics of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region
H. Avakian, QCDN'12, Oct 23
H. Avakian, QCDN'12, Oct 23
Largex limit
Brodsky & Yuan (2006)
LargeNc limit (Pobilitsa)
Do not change sign (isoscalar)
All others change sign u→d (isovector)
H. Avakian, QCDN'12, Oct 23