1. Studies of Partonic Structure using SIDIS
H.Avakian (JLab)
Hall-C collaboration meeting, JLab, Jan 22
JLab, Jan 2010

2. Outline
Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD
Transverse Momentum Distributions (TMDs) of quarks
Spin and spin-azimuthal asymmetries in semi-inclusive DIS
Tests of partonic description
Spin-azimuthal asymmetries
Double spin asymmetries
Future measurements
From JLab12 → EIC
Summary 2
JLab, Jan 2010

3. Transverse Momentum Dependent (TMD) Distributions
Quark polarization
Twist-2
f1u(x,kT)
Nucleon polarization
Real and imaginary parts of the DL≠0 interference contributions
Factorization of kT-dependent PDFs proven at low PT of hadrons (Ji et al)
Twist-3
JLab, Jan 2010

4. SIDIS kinematical plane and observables
U unpolarized
L long.polarized
T trans.polarized
Beam polarization
Target polarization
sin2f moment of the cross section for unpolarized beam and longitudinal target
JLab, Jan 2010

5. Collins mechanism for SSAPT FC
fragmentation of transversely polarized quarks into unpolarized hadrons FC fs fh
Fragmenting quark polarization x y x fS fh PT
fS = p/2+fh x PT fh
fS=p y
HT function related to force on the quark. M.Burkardt (2008) 5
JLab, Jan 2010

6. Sivers mechanisms for SSA-
Sivers mechanisms for SSA PT FS
Correlation between quark transverse momentum and the proton spin fS
fkT
Proton polarization x
HT asymmetries (T-odd)
No leading twist, provide access to quark-gluon correlations 6
JLab, Jan 2010

7. SIDIS: partonic cross sectionskT p┴
PT = p┴ +z kT 7
JLab, Jan 2010

8. Double spin asymmetries and flavor decomposition
Parallel electron & quark spins
Anti-parallel electron & quark spins
HERMES
u-quarks are mainly aligned with proton spin (Du>0)
JLab, Jan 2010

9. SIDIS with JLab at 6 GeV
Scattering of 5.7 GeV electrons off polarized proton and deuteron targets
DIS kinematics,
Q2>1 GeV2, W2>4 GeV2, y<0.85
0.4>z>0.7, MX2>2 GeV2 2
epX
Large PT range and full coverage in azimuthal angle f crucial for studies 9
JLab, Jan 2010

10. Target Single-Spin Asymmetry in Semi-Inclusive n↑(e, e’p+/-)
Reaction on a Transversely Polarized 3He Target e e’ p g*
HRSL
BigBite
16o
30o
Polarized
3He Target
First measurement of the neutron Collins and Sivers asymmetries in SIDIS.
High density polarized 3He target.
Run in Hall A from 10/24/08-2/5/09.
110 shift workers, 7 Ph.D. students.
Cell: Astral
Cell: Maureen
pt ~ 65% (proposal 42%)
JLab, Jan 2010

11. CLAS configuration: EG2000
ep→e’pX e
Longitudinaly polarized target
Polarizations:
Beam: ~70%
NH3 proton ~70%
Target position -55cm
Torus +/-2250
Beam energy ~5.7 GeV p- p+
Polarized NH3/ND3 ( ~5 days)
Polarized NH3/ND3 with IC 60 days 11
JLab, Jan 2010

12. E00-108: Leading-Order x-z factorization
Hall-C
GRV & CTEQ,
@ LO or NLO
Good description for p and d targets for 0.4 < z < 0.65
Closed (open) symbols reflect data after (before) events from coherent r production are subtracted
JLab, Jan 2010

13. A1 PT-dependence in SIDIS
m02=0.25GeV2
mD2=0.2GeV2
M.Anselmino et al hep-ph/
constituent quark model (Pasquini et al).
(2004)
In perturbative limit predicted to be constant
0.79
0.74
p+ ALL can be explained in terms of broader kT distributions for f1 compared to g1
JLab, Jan 2010

14. Quark distributions at large kT: models
JMR model q Dq
MR, R=s,a
Effect of the orbital motion on the q- may be significant (H.A.,S.Brodsky, A.Deur,F.Yuan 2007)
u+<u-
Higher probability to find a quark anti-aligned with proton spin at large kT 14
JLab, Jan 2010

15. Quark distributions at large kT: lattice
Higher probability to find a quark anti-aligned with proton spin at large kT
B.Musch arXiv:
Higher probability to find a d-quark at large kT 15
JLab, Jan 2010

16. Extracting widths from A1
Assuming the widths of f1/g1 x,z and flavor independent
Anselmino et al
Collins et al
Fits to unpolarized data
EMC
JLab, Jan 2010

17. A1 PT-dependence
Lattice A1
Anselmino
Collins
CLAS data suggests that width of g1 is less than the width of f1
New eg1dvcs data allow multidimensional binning to study kT-dependence for fixed x
JLab, Jan 2010

18. kT -distributions in nuclei
bigger effect at large z
CLAS
PT = p┴ +z kT
Hall-C
Higher probability to find a hadron at large PT in nuclei
kT-distributions may be wider in nuclei? 18
JLab, Jan 2010

19. Longitudinal Target SSA measurements at CLAS
ep→e’pX
p1sinf+p2sin2f
CLAS-2000
W2>4 GeV2
Q2>1.1 GeV2
y<0.85
p1= 0.059±0.010
p2=-0.041±0.010
p1=-0.042±0.015
p2=-0.052±0.016
p1=0.082±0.018
p2=0.012±0.019
MX>1.4 GeV
~10% of E data
PT<1 GeV
0.12<x<0.48
0.4<z<0.7
CLAS-2009 (E05-113)
CLAS PRELIMINARY
Data consistent with negative sin2f for p+ 19 19
JLab, Jan 2010

20. Kotzinian-Mulders asymmetry
Transversely polarized quarks in the longitudinally polarized nucleon
curves, cQSM from Efremov et al
CLAS 2009 (projected)
Worm
gear
Measurement of SSAs for pions, provides access to the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995)
Study Collins fragmentation with longitudinally polarized target 20
JLab, Jan 2010

21. What we know about ? Boffi et al, Phys. Rev. D 78 (2008) 034025 21
JLab, Jan 2010

22. Intrinsic transverse momentum densities of the nucleon
Ph. Haegler et al
arXiv:
PhH, B. Musch et al.
arXiv: up
down
genuine effect
of intrinsic transverse
momentum of quarks
GPDs
JLab, Jan 2010

23. CLAS transversely polarized HD-Ice target
HD-Ice target vs std nuclear targets
Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~ mK)
Pros
Small field (∫Bdl~ Tm)
Small dilution (fraction of events from polarized material)
Less radiation length
Less nuclear background (no nuclear attenuation)
Wider acceptance
much better FOM, especially for deuteron
Cons
HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months).
Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA
Additional shielding of Moller electrons necessary (use minitorus)
HD-Ice target at ~2nA ~ NH3 at 5 nA 23
Trento, Nov 12
JLab, Jan 2010

24. CLAS E08-015
Collins SSAs
Anselmino et al (2007)
Boffi et al (2009)
helicity-transversity=pretzelosity
CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function 24
JLab, Jan 2010

25. Electroproduction kinematics: JLab12→EIC
collider experiments
EIC
JLab12 Q2
H1, ZEUS 10-4<xB<0.02
gluons (and quarks)
EIC
EIC 10-4<xB<0.3
fixed target experiments
COMPASS 0.006<xB<0.3
HERMES 0.02<xB<0.3
gluons/valence and sea quarks
JLab  0.1<xB<0.7
valence quarks
Study of high x domain requires high luminosity, low x higher energies
JLab, Jan 2010

26. CLAS12
Wide detector and physics acceptance (current/target fragmentation)
LTCC
PCAL
Lumi = 1035cm-2s-1
High beam polarization 80%
High target polarization 85%
NH3 (30 days) ND3 (50 days) EC
HTCC
FTOF
Replace 2 sectors of LTCC with a proximity RICH detector to identify Kaons approved by JLab PAC34
JLab, Jan 2010

27. Hall-A: Experimental Setup and parameters
G. Cates, E. Cisbani, G.B. Franklin, B. Wojtsekhowski
e+3He→e’+p(K)+X
JLab/HallA
BB: e-arm at 30o
 = 45 msr
GEM Tracker
Gas Cherenkov
Shower
 GMn/PR
SBS: h-arm at 14o
 = 50 msr
GEM tracker
excellent PID / RICH
Hadron CALO
Event rate: ~104×HERMES
60 days of production expected stat. accuracy:
1/10 of proton HERMES
Beam: 50 A, E=8.8 and 11 GeV (80% long. Pol.)
Target: 65% polarized 3He  GEn(2)/PR
 Luminosity: 1.4×1037 cm-2s-1 , 0.05 sr
JLab, Jan 2010

28. E09-002: Executive Summary Hafidi,Gaskell,Dutta SHMS HMS
Experiment: Measure Charged pion electroproduction in semi inclusive DIS off deuterium
SHMS
Conditions:
11 GeV electron beam
10 cm long Liquid deuterium target
Hall C SHMS for electron detection
Hall C HMS for charged pion detection
17 days of beam time
HMS
Objectives: Extract charge symmetry violating valence PDFs (δd – δu) as function of x
for different Q2 bins.
Where and 28
JLab, Jan 2010

29. Flavor decomposition using CLAS12
K.Hafidi et al
10% systematics on asymmetries
JLab, Jan 2010

30. Beam time request: 32 days of beam time in Hall C
Transverse Momentum Dependence of Semi-Inclusive Pion Production PR (Mkrtchyan,Bosted,Ent)
Significant net orbital angular momentum of valence quarks implies significant transverse momentum of quarks
PR : Map the pT dependence (pT ~ L < 0.5 GeV) of p+ and p- production off proton and deuteron targets to measure the kT dependence of up and down quarks
Can only be done using spectrometer setup capable of %-type measurements (an essential ingredient of the global SIDIS program!)
2.9 < Mx2 < 7.8 GeV2
Beam time request: 32 days of beam time in Hall C
Spin-off: Radiative correction modeling for (e,e’p)
Single-spin asymmetries at low pT (< 0.2 GeV)
Low-energy (x,z) factorization for kaons
JLab, Jan 2010

31. A1 PT-dependence in SIDIS E12-07-107
M.Anselmino et al hep-ph/
m02=0.25GeV2
mD2=0.2GeV2
Perturbative limit calculations available for :
J.Zhou, F.Yuan, Z Liang: arXiv:
ALL (p) sensitive to difference in kT distributions for f1 and g1
Wide range in PT allows studies of transition from TMD to perturbative approach 31
JLab, Jan 2010

32. Boer-Mulders Asymmetry with CLAS12 & EICp
5-GeV
50 GeV
Transversely polarized quarks in the unpolarized nucleon
sin(fC) =cos(2fh)
CLAS12
EIC
Perturbative limit calculations available for :
J.Zhou, F.Yuan, Z Liang: arXiv:
Nonperturbative TMD
Perturbative region
CLAS12 and EIC studies of transition from non-perturbative to perturbative regime will provide complementary info on spin-orbit correlations and test unified theory (Ji et al)
JLab, Jan 2010

33. Q2-dependence of beam SSA
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3)
1/Q behavior expected (fixed x bin)
CLAS: E
Hall-C: E
R.Ent & H.Mkrtchyan
Study R and FL
Study for Q2 dependence of beam SSA allows to check the higher twist nature and access quark-gluon correlations.
JLab, Jan 2010

34. PT-dependence of beam SSA E12-06-112
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3)
In the perturbative limit 1/PT behavior expected
4x days, L=1033cm-2s-1
Perturbative region
Nonperturbative TMD
Study for SSA transition from non-perturbative to perturbative regime. EIC will significantly increase the PT range.
JLab, Jan 2010

35. Study the reaction mechanism in SIDIS
x=0.4,z=0.5
CLAS12 PR Puckett et al
Check the NLO predictions in the collinear approximation
Provide input to the analysis of other SIDIS experiments in JLab
JLab, Jan 2010

36. Summary
Measurements of azimuthal dependences of multiplicities as well as double and single spin asymmetries indicate that correlations between spin and transverse motion of quarks may be significant.
PT-dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions.
JLab SIDIS experiments at 6 GeV will significantly improve the statistical precision of longitudinally polarized target data, and will provide new data on transversely polarized target.
Large kinematical acceptance of 11 GeV with L=1035cm-2sec-1 combined with high luminosity L=1037cm-2sec-1 precision measurements at Hall-A/C would allow JLab12 to study in details the 3D structure of the nucleon in the valence region.
JLab, Jan 2010

37. Support slides….
JLab, Jan 2010

38. Transverse momentum dependence of SIDIS
General formalism for (e,e’h) coincidence reaction w. polarized beam:
[A. Bacchetta et al., JHEP 0702 (2007) 093]
(f = azimuthal angle of e’ around the electron beam axis w.r.t. an arbitrary fixed direction)
JLab, Jan 2010

39. CLAS12: Kinematical coverage
epX
SIDIS kinematics
Q2>1GeV2
W2>4 GeV2(10)
y<0.85
MX>2GeV
x=0.3 → Q2=~2 GeV2 (CLAS),
~5 GeV2 (HERMES)
~15 GeV2 (COMPASS)
Large Q2 accessible with CLAS12 are important for separation of HT contributions
JLab, Jan 2010

40. Factorization studies
Simple LO picture in valence region:
Rpd for any z, x!
Rpd+ for any z, pt (if d and u have same pt dependence)! 40
JLab, Jan 2010
Trento, Nov 12

41. SSA with long. polarized target
quark polarization
JLab, Jan 2010

42. SSA with long. polarized target
quark polarization
JLab, Jan 2010

43. SSA with unpolarized target
quark polarization
JLab, Jan 2010

44. SSA with unpolarized target
quark polarization
JLab, Jan 2010

45. Azimuthal moments with unpolarized target
quark polarization 45
JLab, Nov 25
JLab, Jan 2010

46. Azimuthal moments with unpolarized target
quark polarization 46
JLab, Nov 25
JLab, Jan 2010

47. SSA with unpolarized target
quark polarization 47
JLab, Nov 25
JLab, Jan 2010

48. SSA with unpolarized target
quark polarization 48
JLab, Nov 25
JLab, Jan 2010

49. More lattice studies d-quark has wider kT-distribution
d-quark opposite to u
JLab, Jan 2010

50. A1 PT-dependence in SIDIS
0.4<z<0.7
M.Anselmino et al hep-ph/
m02=0.25GeV2
mD2=0.2GeV2
p+ A1 suggests broader kT distributions for f1 than for g1
p- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors
JLab, Jan 2010

51. Dilution factor in SIDIS
Fraction of events from polarized hydrogen in NH3
Nu,Np -total counts from NH3 and carbon normalized by lumi
ru, rp -total areal thickness of hydrogen (in NH3), and carbon target
Cn=Nitr/Carbon ratio (~0.98)
Diff. symbols for diff x-bins p-
Multiple scattering and attenuation in nuclear environment introduces additional PT-dependence for hadrons
JLab, Jan 2010

52. What we know about ?
Boffi EINN2009 52
JLab, Jan 2010