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Prospects for GPD and TMD studies at the JLab Upgrade

This workshop at Jefferson Lab delved into GPDs, TMDs, PDFs, and more, exploring the upgrade's capabilities with detailed kinematic projections and flavor separation techniques.

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Prospects for GPD and TMD studies at the JLab Upgrade

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  1. 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

  2. 3-D Scotty z 2-D Scotty z x y 1-D Scotty Water Calcium probablity Carbon x x GPDs, TMDs & PDFs This Workshop – GPDs, TMDs Deeply Inelastic Scattering, PDFs

  3. Add new hall CHL-2 Enhance equipment in existing halls E= 2.2, 4.4, 6.6, 8.8, 11 GeV Beam polarization Pe > 80% JLab Upgrade to 12 GeV Energy 12 GeV

  4. CLAS12 • Nearly full angle coverage for tracking and g, ndetection • High luminosity, 1035 cm-2s-1 • Concurrent measurement • of deeply virtual exclusive, • semi-inclusive, and inclusive • processes. EC Cerenkov Drift Chambers TOF Cerenkov Torus Central Detector Beamline IEC Design luminosity = 1035cm-2s-1

  5. CLAS12

  6. p- e- e- p g g K+ CLAS12 - Central Detector High Q2, low t ep eK+S0(gL(pp-)) event Silicon tracker, calorimetry, ToF Solenoid magnet, Bcenter = 5 T

  7. 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: dp (GeV/c) 0.003p + 0.001p2 dpT=0.03pT dq (mr) < 1 (>2.5 GeV/c) 8 (1 GeV/c) df (mr) < 3 (> 2.5 GeV/c) 2 (1 GeV/c) Photon detection: Energy range > 150 MeV > 60 MeV dE/E 0.09(EC)/0.04(IEC) 0.06 (1 GeV) dq (mr) 4 (1 GeV) 15 (1 GeV) Neutron detection: heff 0.5 (EC), 0.1 (TOF) 0.04 (TOF) Particle id: e/p >>1000 ( < 5 GeV/c) - >100 ( > 5 GeV/c) - p/K (4s) < 3 GeV/c (TOF) 0.65 GeV/c 3 - 10 GeV/c (CC) p/p (4s) < 5 GeV/c (TOF) 1.2 GeV/c 3 - 10 GeV/c (CC) K/p(4s) < 3.5 GeV/c (TOF) 0.9 GeV/c

  8. H1, ZEUS Deeply Virtual Exclusive Processes - Kinematics Coverage of the 12 GeV Upgrade H1, ZEUS 27 GeV 11 GeV 11 GeV 200 GeV JLab Upgrade JLab @ 12 GeV COMPASS W = 2 GeV HERMES Study of high xB domain requires high luminosity 0.7

  9. ep egp Q2 > 2.5 GeV2 Central Detector Forward Detector ep ep+X Acceptance for DVCS, SIDIS qg xB = 0.35 EC IEC Q2

  10. Ds 2s ep epg s+ - s- s+ + s- A = = x = xB/(2-xB) k = t/4M2 Separating GPDs through polarization Polarized beam, unpolarized target: ~ ~ DsLU~ sinf{F1H+ x(F1+F2)H+kF2E}df H, H, E Kinematically suppressed Unpolarized beam, longitudinal target: ~ ~ H, H DsUL~ sinf{F1H+x(F1+F2)(H+ … }df Unpolarized beam, transverse target: H, E DsUT~ sinf{k(F2H – F1E) + …..}df

  11. ALU B DVCS/BH- Beam Asymmetry ~ ~ Ee = 11 GeV DsLU~ sinf{F1H+ x(F1+F2)H+kF2E}df ALU CLASpreliminary E=5.75 GeV <Q2> = 2.0GeV2 <x> = 0.3 <-t> = 0.3GeV2 f [rad]

  12. Q2=5.5GeV2 xB = 0.35 -t = 0.25 GeV2 CLAS12 - DVCS/BH- Beam Asymmetry Ee = 11 GeV Luminosity = 720fb-1

  13. e p epg L = 1x1035 T = 2000 hrs DQ2 = 1 GeV2 Dx = 0.05 CLAS12- DVCS/BH Beam Asymmetry E = 11 GeV DsLU~sinfIm{F1H+..}df Sensitive to GPDH Selected Kinematics

  14. Q2=3.5 GeV2 bval=bsea=1 MRST02 NNLO distribution • Other kinematics measured concurrently GPDs H from expected DVCS ALUdata p

  15. L = 2x1035 cm-2s-1 T = 1000 hrs DQ2 = 1GeV2 Dx = 0.05 e p epg E = 11 GeV E=5.75 GeV AUL CLAS preliminary <Q2> = 2.5GeV2 <x> = 0.25 <-t> = 0.25GeV2 CLAS12-DVCS/BH Target Asymmetry Longitudinally polarized target ~ Ds~sinfIm{F1H+x(F1+F2)H...}df

  16. Sample kinematics e p epg E = 11 GeV Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 • Asymmetry highly sensitive to the u-quark contributions to proton spin. CLAS12- DVCS/BH Target Asymmetry Transverse polarized target Ds ~ sinfIm{k1(F2H– F1E) +…}df AUTx Target polarization in scattering plane AUTy Target polarization perpedicular to scattering plane

  17. GPDs – Flavor separation DVMP DVCS long. only hard gluon hard vertices M = r0/r+ select H, E, for u/d flavors M = p, h, K select H, E Photons cannot separate u/d quark contributions.

  18. xB = 0.3-0.4 -t = 0.2-0.3GeV2 sL sT Other bins measured concurrently CLAS12– L/T Separationep epro (p+p-) Projections for 11 GeV (sample kinematics) • Test of Bjorken scaling • Power corrections?

  19. Q2=5 GeV2 Exclusiver0 production on transverse target 2D (Im(AB*))/p T AUT = - |A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2 A~ 2Hu + Hd r0 B~ 2Eu + Ed Eu, Edneeded for angular momentum sum rule. r0 K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001 B

  20. CLAS 5.7 GeV r+ n Exclusive r+with transverse target Strong sensitivity to d-quark contributions. A~ Hu - Hd B ~ Eu - Ed AUT r+

  21. 1 1 1 [ ] ò = - J G = x + x J q xdx H q( x , , 0 ) E q( x , , 0 ) 2 2 - 1 X. Ji, Phy.Rev.Lett.78,610(1997) Quark Angular Momentum Sum Rule With GPDs Hu, Hd, Eu, Edobtain access to total quark contribution to proton angular momentum. Large x contributions important.

  22. Wpu(x,k,r) “Parent” Wigner distributions d3r TMD TMD PDFs: fpu(x,kT),g1,f┴1T, h┴1L Measure momentum transfer to quark. Transverse Momentum Dependent PDFs (TMDs) Probability to find a quark u in a nucleon P with a certain polarization in a position r and momentum k d2kT (FT) GPD GPDs: Hpu(x,x,t), Epu(x,x,t),… Measure momentum transfer to nucleon.

  23. SIDIS at leading twist e Boer e p Mulders e p transversity Sivers 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)

  24. Azimuthal Asymmetry – Sivers Effect Originates in the quark distribution. It is measured in the azimuthal asymmetry with transverse polarized target. sin(f-fs) f1TD1 T AUT ~ k Requires: non-trivial phase from the FSI + interference between different helicity states (S. Brodsky)

  25. sin(f-fs) (P /M)AUT T SIDIS Azimuthal Asymmetry - Sivers effect • Probes orbital angular momentum of quarks by measuring the imaginary part ofs-p-wave interference in the amplitude. T • Extraction of Sivers function f1T from asymmetry.

  26. CLAS12- Sivers function from AUT (p0) Efremov et al (large xB behavior of f1T from GPD E) In large Nc limit: F1T=∑qeq2f1T┴q f1Tu = -f1Td CLAS12 projected CLAS12 projected xB xB

  27. sin(f+fs) sUT~ k h1H1 T Azimuthal Asymmetry - Collins Effect • Access to transversity distribution and fragmentation of polarized quarks.

  28. x=0.4 1.5 fm 0 CAT scan slice of human abdomen z -1.5 y x=0.9 1 fm flavor polarization 0 X. Ji -1 u-quark charge density distribution Tomographic Images of the Nucleon dX(x,b ) uX(x,b ) T T M. Burkardt Ed(x,t) Eu(x,t)

  29. DDVCS DVCS asymmetry Cross section DDVC rates reduced by more than factor 200 e-p e-pe+e- Double DVCS (DDVCS)

  30. e+ e- e- p CLAS12 – Acceptance for DDVCS

  31. 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.

  32. New Collaborators are welcome!

  33. Additional Slides

  34. Sivers effect in the target fragmentation xF>0 (current fragmentation) xF<0 (target fragmentation) xF- momentum in the CM frame Wide kinematic coverage of CLAS12 allows studies of hadronization in the target fragmentation region

  35. T T sUL ~ k h1LH1 KM 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.

  36. T T sUL ~ (1-y) h1LH1 KM 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.

  37. ` CLAS12-L(1115) Polarization E = 11 GeV ep eL(pp-)X (SIDIS) K K*(892)

  38. e 1 Λ p 2 L polarization in the target fragmentation e’

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