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Prospects for GPD and TMD studies at the JLab Upgrade. Volker D. Burkert Jefferson Lab. Introduction JLab Upgrade and CLAS12 GPDs from DVCS and DVMP TMDs from SIDIS and SSA Summary. SIR Workshop – Jefferson Lab, May 17-20, 2005. 3-D Scotty. z. 2-D Scotty. z. x. y. - PowerPoint PPT Presentation
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Prospects for GPD and TMD studies at the JLab Upgrade
Volker D. Burkert Jefferson Lab
SIR Workshop – Jefferson Lab, May 17-20, 2005
Introduction JLab Upgrade and CLAS12 GPDs from DVCS and DVMP TMDs from SIDIS and SSA Summary
z
y
3-D Scotty
x
1-D Scotty
x
prob
abli
tyCalcium
Water
Carbon
2-D Scottyz
x
GPDs, TMDs & PDFs
Deeply Inelastic Scattering,PDFs
This Workshop – GPDs, TMDs
JLab Upgrade to 12 GeV Energy
CHL-2CHL-2
Enhance equipment in existing halls
Add new Add new hallhall
12 GeV
Beam polarizationPe > 80%
E= 2.2, 4.4, 6.6, 8.8, 11 GeV
CLAS12 EC
TOF
Cerenkov
Torus
Drift Chambers
Cerenkov
Central Detector
BeamlineIEC
Design luminosity = 1035cm-2s-1
Nearly full angle coverage for tracking and ndetection High luminosity, 1035 cm-2s-1
Concurrent measurement of deeply virtual exclusive, semi-inclusive, and inclusive processes.
CLAS12
High Q2, low t ep eK+p event
K+
e-
CLAS12 - Central Detector
p
e-
Silicon tracker, calorimetry, ToF Solenoid magnet,Bcenter = 5 T
CLAS 12 - Expected Performance Forward Detector Central Detector
Angular coverage: Tracks (inbending) 8o - 40o 40o - 135o
Tracks (outbending) 5o - 40o 40o - 135o Photons 2o - 40o 40o - 135o
Track resolution:p (GeV/c) 0.003p + 0.001p2 pT=0.03pT
(mr) < 1 (>2.5 GeV/c) 8 (1 GeV/c) (mr) < 3 (> 2.5 GeV/c) 2 (1 GeV/c) Photon detection:Energy range > 150 MeV > 60 MeV E/E 0.09(EC)/0.04(IEC) 0.06 (1 GeV)(mr) 4 (1 GeV) 15 (1 GeV)Neutron detection:eff 0.5 (EC), 0.1 (TOF) 0.04 (TOF) Particle id:e/ >>1000 ( < 5 GeV/c) -
>100 ( > 5 GeV/c) -/K (4) < 3 GeV/c (TOF) 0.65 GeV/c
3 - 10 GeV/c (CC)p5 GeV/c (TOF) 1.2 GeV/c
3 - 10 GeV/c (CC)K/p() < 3.5 GeV/c (TOF) 0.9 GeV/c
Deeply Virtual Exclusive Processes - Kinematics Coverage of the 12 GeV Upgrade
H1, ZEUS
JLab Upgrade
11 GeV
H1, ZEUS
JLab @ 12 G
eV11 GeV27
GeV
200
GeV
W =
2 GeV
Study of high xB domain requires high luminosity
0.7
HERMES
COMPASS
Q2 > 2.5 GeV2
Forward Detector
Central Detector
ep ep
Acceptance for DVCS, SIDIS
ep e+X
xB = 0.35
EC
IEC
Q2
Separating GPDs through polarization
LU~ sin{F1H + (F1+F2)H +kF2E}d~
Polarized beam, unpolarized target:
Unpolarized beam, longitudinal target:
UL~ sin{F1H+(F1+F2)(H + … }d~
Unpolarized beam, transverse target:
UT~ sin{k(F2H – F1E) + …. }d
= xB/(2-xB)
k = t/4M2
H, H, E
Kinematically suppressed
H, H~
H, E
A =
=
~
ep ep
DVCS/BH- Beam Asymmetry
Ee = 11 GeV
ALUALU
E=5.75 GeV
<Q2> = 2.0GeV2
<x> = 0.3<-t> = 0.3GeV2
CLAS preliminary
[rad]
B
LU~ sin{F1H + (F1+F2)H +kF2E}d~~
CLAS12 - DVCS/BH- Beam Asymmetry
Ee = 11 GeV
Q2=5.5GeV2
xB = 0.35 -t = 0.25 GeV2
Luminosity = 720fb-1
CLAS12 - DVCS/BH Beam Asymmetry
L = 1x1035
T = 2000 hrsQ2 = 1 GeV2
x = 0.05
E = 11 GeV
Selected Kinematics
Sensitive to GPD H
LU~sinIm{F1H+.}d
e p ep
GPDs H from expected DVCS ALU data
bval=bsea=1
MRST02 NNLOdistribution
Q2=3.5 GeV2
Other kinematics measured concurrently
CLAS12 - DVCS/BH Target Asymmetry
e p epLongitudinally polarized
target
~sinIm{F1H+(F1+F2)H...}d~
E = 11 GeVL = 2x1035 cm-2s-1
T = 1000 hrsQ2 = 1GeV2
x = 0.05
CLAS preliminaryE=5.75 GeV
AU
L
<Q2> = 2.5GeV2
<x> = 0.25<-t> = 0.25GeV2
CLAS12 - DVCS/BH Target Asymmetry
Asymmetry highly sensitive to the u-quark contributions to proton spin.
Transverse polarized target
e p ep
~ sinIm{k1(F2H – F1E) +…}d
Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2E = 11 GeVSample kinematics
AUTx Target polarization in scattering plane
AUTy Target polarization perpedicular to scattering plane
DVCSDVCS DVMPDVMP
GPDs – Flavor separation
hard vertices
hard gluon
Photons cannot separate u/d quarkcontributions.
long. only
M = select H, E, for u/d flavorsM = , K select H, E
CLAS12 – L/T Separation ep ep
L
T
xB = 0.3-0.4 -t = 0.2-0.3GeV2
Other bins measured concurrently
Projections for 11 GeV(sample kinematics)
Test of Bjorken scaling
Power corrections?
Exclusive production on transverse target
2 (Im(AB*))/ T
t/4m2) - ReUT
A ~ 2Hu + Hd
B ~ 2Eu + Ed0
K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001
Q2=5 GeV2
Eu, Ed needed forangular momentum sum rule. 0
B
AUT
Exclusive with transverse target
Strong sensitivity to d-quark contributions.
A ~ Hu - Hd
B ~ Eu - Ed
+
CLAS5.7 GeV
n
J G = 1
1
)0,,q()0,,q(2
1
2
1 xE xHxdxJ q
X. Ji, Phy.Rev.Lett.78,610(1997)
Quark Angular Momentum Sum Rule
With GPDs Hu, Hd, Eu, Ed obtain access to total quark contribution to proton angular momentum. Large x contributions important.
Wpu(x,k,r) “Parent” Wigner distributions
d 2kT(FT)
GPDs: Hpu(x,,t), Ep
u(x,,t),…
GPD
Measure momentum transfer to nucleon.
Probability to find a quark u in a nucleon P with a certain polarization in a position r and momentum k
TMD PDFs: fpu(x,kT),g1,f┴
1T, h┴1L
d3 r
Measure momentum transfer to quark.
TMD
Transverse Momentum Dependent PDFs (TMDs)
SIDIS at leading twist
e
e
e
p
p
Sivers transversity
Mulders
Boer
Off-diagonal PDFs vanish if quarks only in s-state! In addition T-odd PDFs require FSI (Brodsky et al., Collins, Ji et al. 2002)
Originates in the quark distribution. It is measured in the azimuthal asymmetry with transverse polarized target.
Requires: non-trivial phase from theFSI + interference between different helicity states (S. Brodsky)
Azimuthal Asymmetry – Sivers Effect
f1T D1AUT ~ k sins)
T
SIDIS Azimuthal Asymmetry - Sivers effect
Extraction of Sivers function f1T from asymmetry.
Probes orbital angular momentum of quarks by measuring the
imaginary part of s-p-wave interference in the amplitude.
T(P
/M
)AU
Tsin s
)
T
CLAS12 - Sivers function from AUT (0)
F1T=∑qeq2f1T
┴qIn large Nc limit:
f1Tu = -f1T
d
Efremov et al(large xB behavior of
f1T from GPD E)
xB xB
CLAS12projected
CLAS12projected
Azimuthal Asymmetry - Collins Effect
Access to transversity distribution and fragmentation of polarized quarks.
UT ~ k h1H1
sins)
T
dX(x,b )
T
Eu(x,t)Ed(x,t)
M. Burkardt
Tomographic Images of the Nucleon
uX(x,b )T
flavor polarization
x=0.41.5
0
-1.5
fm
x=0.91
0
-1
fm
X. Ji
u-quark charge density distribution
y
z
CAT scan sliceof human abdomen
Double DVCS (DDVCS)
Cross section
DVCSasymmetry
DDVCS
DDVC rates reduced by more than factor 200
e-p e-pe+e-
CLAS12 – Acceptance for DDVCS
p
e-
e-
e+
Summary
The JLab 12 GeV Upgrade is essential for the study of nucleon structure in the valence region with high precision:
- deeply virtual exclusive processes (DVCS, DVMP) - semi-inclusive meson production with polarized beam and polarized targets
Provide new and deeper insight into - quark orbital angular momentum contributions to the nucleon spin- 3D structure of the nucleon’s interior and correlations- quark flavor polarization- …..
CLAS12 will be world wide the only full acceptance, general purpose detector for high luminosity electron scattering experiments, and is essential for the GPD/TMD program.
New Collaborators are welcome!
Additional Slides
Sivers effect in the target fragmentation
xF<0 (target fragmentation)
xF>0 (current fragmentation)
xF - momentum in the CM frame
Wide kinematic coverage of CLAS12 allows studies of hadronization in the target fragmentation region
Collins Effect and Kotzinian-Mulders Asymmetry
Measures the Collins fragmentation with longitudinally polarized target. Access to the real part of s-p wave interference amplitudes.
UL ~ k h1LH1KM
T T
Collins Effect and Kotzinian-Mulders Asymmetry
Measures the Collins fragmentation with longitudinally polarized target. Access to the real part of s-p wave interference amplitudes.
UL ~ (1-y) h1LH1KM
T T
`
CLAS12 - (1115) Polarization
ep e(pX (SIDIS)
K*(892)K
E = 11 GeV
polarization in the target fragmentation
p
e
Λ1 2
e’