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

Studies of Partonic Structure using SIDIS
H.Avakian (JLab)
Hall-C collaboration meeting, JLab, Jan 22
JLab, Jan 2010
1
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
JLab, Jan 2010
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Transverse Momentum Dependent (TMD) Distributions
Twist-2
Quark polarization
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
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SIDIS kinematical plane and observables
Beam polarization
Target polarization
U unpolarized
L long.polarized
T trans.polarized
sin2f moment of the cross section for
unpolarized beam and longitudinal target
JLab, Jan 2010
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Collins mechanism for SSA
FC
fs
PT
fragmentation of transversely polarized
quarks into unpolarized hadrons
fh
FC
Fragmenting
quark polarization
x
fS = p/2+fh
y
PT
fS
fh
x
PT
fh
y
fS=p
x
HT function related to force on
the quark. M.Burkardt (2008)
JLab, Jan 2010
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Sivers mechanisms for SSA
FS
fS
PT
-
Correlation between quark transverse
momentum and the proton spin
fkT
Proton
polarization
x
HT asymmetries (T-odd)
No leading twist, provide access to quark-gluon correlations
JLab, Jan 2010
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SIDIS: partonic cross sections
p┴
PT = p┴ +z kT
JLab, Jan 2010
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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
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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
epX
2
Large PT range and full coverage in azimuthal angle f crucial for studies
JLab, Jan 2010
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Target Single-Spin Asymmetry in Semi-Inclusive n↑(e, e’p+/-)
E06-010:
Reaction on a Transversely Polarized 3He Target
16o
g*
HRSL
p
Polarized
3He Target
BigBite
30o
• 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.
e’
e
pt ~ 65% (proposal 42%)
Cell: Astral
Cell: Maureen
JLab, Jan 2010
10
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
pp+
1) Polarized NH3/ND3 ( ~5 days)
2) Polarized NH3/ND3 with IC 60 days
JLab, Jan 2010
11
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
12
A1 PT-dependence in SIDIS
m02=0.25GeV2
mD2=0.2GeV2
M.Anselmino et al
hep-ph/0608048
constituent quark model (Pasquini et al).
(2004)
In perturbative limit predicted to be constant
p+ ALL can be explained in terms of broader kT
distributions for f1 compared to g1
JLab, Jan 2010
0.79
0.74
0.74
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Quark distributions at large kT: models
q
JMR model
Dq
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
JLab, Jan 2010
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Quark distributions at large kT: lattice
Higher probability to find a
quark anti-aligned with
proton spin at large kT
B.Musch arXiv:0907.2381
Higher probability to find a
d-quark at large kT
JLab, Jan 2010
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Extracting widths from A1
Assuming the widths of f1/g1 x,z and flavor independent
EMC
Fits to unpolarized data
Anselmino et al
Collins et al
JLab, Jan 2010
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A1
A1 PT-dependence
Lattice
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 17
JLab, Jan 2010
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?
JLab, Jan 2010
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Longitudinal Target SSA measurements at CLAS
ep→e’pX
p1sinf+p2sin2f
p1= 0.059±0.010
p2=-0.041±0.010
p1=-0.042±0.015
p2=-0.052±0.016
CLAS-2000
W2>4 GeV2
Q2>1.1 GeV2
y<0.85
p1=0.082±0.018
p2=0.012±0.019
MX>1.4 GeV
PT<1 GeV
0.12<x<0.48
0.4<z<0.7
~10% of E05-113 data
CLAS-2009 (E05-113)
CLAS PRELIMINARY
Data consistent with negative sin2f for p+
JLab, Jan 2010
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Kotzinian-Mulders asymmetry
Transversely polarized
quarks in the longitudinally
polarized nucleon
Worm
gear
curves, cQSM
from Efremov et al
CLAS 2009 (projected)
•Measurement of SSAs for pions, provides access to the RSMT TMD (RalstonSoper (1979), Mulders-Tangerman (1995)
•Study Collins fragmentation with longitudinally polarized target
JLab, Jan 2010
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What we know about
Boffi et al, Phys. Rev. D 78 (2008) 034025
JLab, Jan 2010
?
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Intrinsic transverse momentum densities of the nucleon
Ph.
PhH,Haegler
B. Muschet
et al
al.
arXiv:0908.1283
arXiv:0908.1283
down
up
GPDs
genuine effect
of intrinsic transverse
momentum of quarks
JLab, Jan 2010
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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~500-750mK)
Pros
1. Small field (∫Bdl~0.005-0.05Tm)
2. Small dilution (fraction of events from polarized material)
3. Less radiation length
4. Less nuclear background (no nuclear attenuation)
HD-Ice target at ~2nA
5. Wider acceptance
~ NH3 at 5 nA
much better FOM, especially for deuteron
Cons
1. HD target is highly complex and there is a need for redundancy due to the very
long polarizing times (months).
2. Need to demonstrate that the target can remain polarized for long periods with an
electron beam with currents of order of 1-2 nA
3. Additional shielding of Moller electrons necessary (use minitorus)
JLab,
Trento,
Jan
Nov
2010
12
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Collins SSAs
Anselmino et al (2007)
CLAS E08-015
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
JLab, Jan 2010
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Electroproduction kinematics: JLab12→EIC
Q2
collider experiments
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
EIC
HERMES 0.02<xB<0.3
gluons/valence and sea quarks
JLab12
JLab
 0.1<xB<0.7
JLab@12GeV
valence quarks
Study of high x domain requires high
luminosity, low x higher energies
JLab, Jan 2010
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CLAS12
LTCC
PCAL
Wide detector and physics
acceptance (current/target
fragmentation)
Lumi = 1035cm-2s-1
High beam polarization 80%
High target polarization 85%
NH3 (30 days) ND3 (50 days)
HTCC
FTOF
EC
Replace 2 sectors of LTCC with a proximity RICH
detector to identify Kaons approved by JLab PAC34
JLab, Jan 2010
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Hall-A: Experimental Setup and parameters
G. Cates, E. Cisbani, G.B.
e+3He→e’+p(K)+X
JLab/HallA
Franklin, B. Wojtsekhowski
BB: e-arm at 30o
 = 45 msr
GEM Tracker
Gas Cherenkov
Shower
 GMn/PR-09-019
SBS:h-arm at 14o
 = 50 msr
GEM tracker
excellent PID / RICH
Hadron CALO
Beam: 50 mA, E=8.8 and 11 GeV (80% long. Pol.)
Target: 65% polarized 3He  GEn(2)/PR-09-016
 Luminosity: 1.4×1037 cm-2s-1 , 0.05 sr
JLab, Jan 2010
Event rate: ~104×HERMES
60 days of production
expected stat. accuracy:
1/10 of proton HERMES
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E09-002: Executive Summary
Experiment:
Hafidi,Gaskell,Dutta
Measure Charged pion electroproduction in semi inclusive DIS off deuterium
D
RMeas
(x,z) 
RY (x,z) 

Conditions:
4RY (x,z) -1
1- RY (x,z)
SHMS
Dp -
Y (x,z)
Dp +
Y (x,z)

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
Objectives:
HMS
Extract charge symmetry violating valence PDFs (δd – δu) as function of x
for different Q2 bins.
Where d  d p - u n
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

and u  u p - d n
JLab, Jan 2010
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Flavor decomposition using CLAS12
E12-09-007
K.Hafidi et al
10% systematics on asymmetries
JLab, Jan 2010
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Transverse Momentum Dependence of Semi-Inclusive
Pion Production PR12-09-017 (Mkrtchyan,Bosted,Ent)
Significant net orbital angular momentum of valence
quarks implies significant transverse momentum of quarks
PR12-09-017: 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
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A1 PT-dependence in SIDIS
E12-07-107
M.Anselmino et al
hep-ph/0608048
m02=0.25GeV2
mD2=0.2GeV2
Perturbative limit calculations
available for
:
J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238
•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
JLab, Jan 2010
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Boer-Mulders Asymmetry with CLAS12 & EIC
5-GeV
-
e
p
50 GeV
E12-06-112
Transversely polarized quarks in
the unpolarized nucleon
sin(fC) =cos(2fh)
CLAS12
EIC
Perturbative limit calculations
available for
Nonperturbative TMD
Perturbative region
:
J.Zhou, F.Yuan, Z Liang:
arXiv:0909.2238
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
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Q2-dependence of beam SSA
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3)
1/Q behavior
expected (fixed x bin)
CLAS: E12-06-112
Hall-C: E12-06-104
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
33
PT-dependence of beam SSA
E12-06-112
ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3)
In the
perturbative limit
1/PT behavior
expected
4x60 100 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
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Study the reaction mechanism in SIDIS
x=0.4,z=0.5
CLAS12 PR10-010 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
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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 CLAS12@ 11 GeV with L=1035cm-2sec1 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
36
Support slides….
JLab, Jan 2010
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Transverse momentum dependence of SIDIS
General formalism for (e,e’h) coincidence reaction w. polarized beam:
[A. Bacchetta et al., JHEP 0702 (2007) 093]
ds
2
y2  g 2 
1 +  FUU ,T + FUU , L +

2
2
dxdyddzdfh dPh,t xyQ 2(1 -  )  2 x 
{
cosfh
cos( 2fh )
sin fh
2 (1 +  ) cosfh FUU
+  cos(2fh ) FUU
+ e 2 (1 +  ) sin fh FLU
}
(f = azimuthal angle of e’ around the electron beam axis w.r.t. an arbitrary fixed direction)
JLab, Jan 2010
38
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
39
Factorization studies
Simple LO picture in valence region:
RRpd+
pt (if
forz,any
z, dx!and u have same pt dependence)!
pd- for any
JLab,
Trento,
Jan
Nov
2010
12
40
SSA with long. polarized target
quark polarization
JLab, Jan 2010
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SSA with long. polarized target
quark polarization
JLab, Jan 2010
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SSA with unpolarized target
quark polarization
JLab, Jan 2010
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SSA with unpolarized target
quark polarization
JLab, Jan 2010
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Azimuthal moments with unpolarized target
quark polarization
JLab,
JLab,Jan
Nov2010
25
45
Azimuthal moments with unpolarized target
quark polarization
JLab,
JLab,Jan
Nov2010
25
46
SSA with unpolarized target
quark polarization
JLab,
JLab,Jan
Nov2010
25
47
SSA with unpolarized target
quark polarization
JLab,
JLab,Jan
Nov2010
25
48
More lattice studies
d-quark has wider kT-distribution
d-quark opposite to u
JLab, Jan 2010
49
A1 PT-dependence in SIDIS
0.4<z<0.7
M.Anselmino et al
hep-ph/0608048
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
50
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
Diff. symbols
for(~0.98)
diff x-bins
p-
Multiple scattering and attenuation in
nuclear environment introduces
additional PT-dependence for hadrons
JLab, Jan 2010
51
What we know about
?
Boffi EINN2009
JLab, Jan 2010
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