prospects for gpd and tmd studies at the jlab upgrade

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

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1-D Scotty

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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’