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Harut Avakian

Feasibility Studies for EIC Nucleon Program. Harut Avakian. "Electron-ion colliders". 28 September, 2009 Milos Conference Center George Eliopoulos Milos Island, Greece. Outline. Physics motivation TMDs and spin-orbit correlations Accessing TMDs in semi-inclusive DIS

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Harut Avakian

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  1. Feasibility Studies for EIC Nucleon Program Harut Avakian "Electron-ion colliders" 28 September, 2009 Milos Conference Center George Eliopoulos Milos Island, Greece H. Avakian, Milos, Sep 28

  2. Outline Physics motivation TMDs and spin-orbit correlations Accessing TMDs in semi-inclusive DIS Higher twists in SIDIS GPDs and quark-gluon imaging Accessing GPDs in hard exclusive processes Higher twists in hard exclusive processes Projections for transverse SSAs at EIC and comparison with JLAB12 Summary H. Avakian, Milos, Sep 28

  3. HERA 27 GeV Q2 Q2 EIC ENC ENC JLab (upgraded) EIC compass hermes ENC JLab@6GeV JLab12 Electroproduction kinematics: HERA→JLab→EIC collider experiments H1, ZEUS(EIC) 10-4<xB<0.02 (0.3):gluons (and quarks) in the proton fixed target experiments COMPASS, HERMES  0.006/0.02<xB<0.3 : gluons/valence and sea quarks JLab/JLab@12GeV  0.1<xB<0.7: valence quarks Study of high x domain requires high luminosity, low x higher energies H. Avakian, Milos, Sep 28

  4. Single hadron production in hard scattering Target fragmentation Current fragmentation semi-inclusive exclusive semi-exclusive h h FF h DA DA h M PDF GPD PDF 1 -1 xF 0 Fracture Functions kT-dependent PDFs Generalized PDFs xF>0 (current fragmentation) h xF<0 (target fragmentation) xF- momentum in the CM frame Measurements in different kinematical regions provide complementary information on the complex nucleon structure. 4 H. Avakian, Milos, Sep 28

  5. Wpu(k,rT) “Mother” Wigner distributions d2kT d2rT GPDs/IPDs TMD PDFs f1u(x,kT), .. h1u(x,kT) d2kT Structure of the Nucleon quark polarization PDFs f1u(x), .. h1u(x) • Gauge invariant definition (Belitsky,Ji,Yuan 2003) • Universality of kT-dependent PDFs (Collins,Metz 2003) • Factorization for small kT. (Ji,Ma,Yuan 2005) H. Avakian, Milos, Sep 28

  6. EIC medium energy EIC@JLab EIC@RHIC Main Features • Electron energy: 3-11 GeV • Proton energy: 12-60 GeV • More symmetric kinematics provides better resolution and particle id • Luminosity: few x 1034 cm-2 s-1 • in range around s ~ 1000 GeV2 • Polarized electrons and light ions • longitudinal and transverse • Limited R&D needs • 3 interaction regions (detectors) • Potential upgrade with high-energy ring • Electron energy: 4-20 GeV • Proton energy: 50-250 GeV • More symmetric kinematics provides better resolution and particle id • Luminosity: ~ 1033 cm-2 s-1 • in range around s ~ 1000-10000 GeV2 • Polarized electrons and light ions • longitudinal and transverse • Limited R&D needs • ? interaction regions (detectors) • 90% of hardware can be reused H. Avakian, Milos, Sep 28

  7. Current Ideas for EIC • Present focus of interest (in the US) are the (M)EIC and Staged MeRHIC versions, with s up to 2650 and 4000, resp. • Most of the slides are for a “generic” US version of an EIC (5x50 or 4x60): • polarized beams (longitudinal and transverse, > 70%) • luminosities of at least 1033 ( ~1034 for exclusive processes) • energies up to 10 x 250, or s = 10000 H. Avakian, Milos, Sep 28

  8. The Detector Wide kinematic coverage and large acceptance would allow studies of hadronization both in the target and current fragmentation regions H. Avakian, Milos, Sep 28

  9. Beam polarization Target polarization SIDIS kinematical plane and observables PT U unpolarized L long.polarized T trans.polarized sin(f-fS) moment of the cross section for unpolarized beam and transverse target H. Avakian, Milos, Sep 28

  10. SIDIS: partonic cross sections kT Is this good enough for flavor decomposition? p┴ PT = p┴+zkT 10 H. Avakian, Milos, Sep 28

  11. Quark longitudinal polarization BBS/LSS no OAM q Dq Du/u JMR model MR, R=s,a (dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian BBS/LSS with OAM Effect of the orbital motion on the q- may be significant (H.A.,S.Brodsky, A.Deur,F.Yuan 2007) For given xthesignof the polarization is changing at large kT 11 H. Avakian, Milos, Sep 28

  12. A1 PT-dependence in SIDIS Perturbative limit calculations available for : J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238 M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 • 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 12 H. Avakian, Milos, Sep 28

  13. Flavor Decomposition @ EIC • quark polarization Dq(x) • first 5-flavor separation H. Avakian, Milos, Sep 28

  14. Precisely image the sea quarks Spin-Flavor Decomposition of the Light Quark Sea Flavor decomposition will be performed using binning in PT H. Avakian, Milos, Sep 28

  15. The Gluon Contribution to the Proton Spin Projected data on Dg/g with an EIC, via g + p  D0 + X K- + p+ assuming vertex separation of 100 mm. Bruell,Ent RHIC-Spin • Uncertainties in xDg smaller than 0.01 • Measure 90% of DG (@ Q2 = 10 GeV2) H. Avakian, Milos, Sep 28

  16. Measuring the charm content of the proton Within the FFNS (no heavy quarks), the leading mechanism contributing to F2, FLandFA. At high Q2 with heavy quarks (VFNS), there is additional contribution to F2, but not toFLandFA! The heavy-quark content of the proton is due to resummation of the mass logarithms of the type αs ln(Q2 /m2)and thus, closely related to behavior of asymptotic perturbative series for high Q2. • N.Ya.Ivanov, Nucl. Phys. B 814 (2009), 142 H. Avakian, Milos, Sep 28

  17. Resummation for A= 2xFA/ F2 • L.N. Ananikyan, N.Ya. Ivanov,. Nucl.Phys.B762:256-283,2007. N.Ya.Ivanov, Nucl. Phys. B 814 (2009), 142 CTEQ PDFs used for estimates • The mass logarithms resummation (or heavy-quark densities) • should reduce the pQCD predictions for R= FL/ FT and A=2xFA/ F2. • cos2f moment in charm meson production provides access to charm densities • N.Ya.Ivanov, Nucl. Phys. B 814 (2009), 142 H. Avakian, Milos, Sep 28

  18. EIC: Kinematics Coverage e p xF>0 (CFR) 5 GeV 50 GeV xF<0 ( TFR) e’p+X all xF>0 z>0.3 EIC-MC EIC-MC (PYTHIA based) Major part of current particles at large angles in Lab frame (PID at large angles crucial). H. Avakian, Milos, Sep 28

  19. fs y PT fS= p/2+fh fS fh x fh y PT fS=p x Collins mechanism for SSA PT FC fragmentation of transversely polarized quarks into unpolarized hadrons FC fh Fragmenting quark polarization x HT function related to force on the quark. M.Burkardt (2008) 19 H. Avakian, Milos, Sep 28

  20. Sivers mechanisms for SSA fS SIDIS Drell-Yan - M.Burkardt (2000) HT asymmetries (T-odd) PT FS Correlation between quark transverse momentum and the proton spin fkT Proton polarization x No leading twist, provide access to quark-gluon correlations 20 H. Avakian, Milos, Sep 28

  21. PT-dependence of beam SSA 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. H. Avakian, Milos, Sep 28

  22. Q2-dependence of beam SSA ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3) 1/Qbehavior expected (fixed x bin) Study for Q2 dependence of beam SSA allows to check the higher twist nature and access quark-gluon correlations. H. Avakian, Milos, Sep 28

  23. e p 5-GeV 50 GeV - Boer-Mulders Asymmetry with CLAS12 & EIC 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:0909.2238 Nonperturbative TMD Perturbative region CLAS12 and EICstudies of transition from non-perturbative to perturbative regime will provide complementary info on spin-orbit correlations and test unified theory (Ji et al) H. Avakian, Milos, Sep 28

  24. Sivers effect: pion electroproduction GRV98, Kretzer FF (4par) S. Arnold et al arXiv:0805.2137 M. Anselmino et al arXiv:0805.2677 GRV98, DSS FF (8par) • EIC measurements at small x will pin down sea contributions to Sivers function H. Avakian, Milos, Sep 28

  25. Sivers effect: Kaon electroproduction EIC CLAS12 • At small x of EIC Kaon relative rates higher, making it ideal place to study the Sivers asymmetry in Kaon production (in particular K-). • Combination with CLAS12 data will provide almost complete x-range. H. Avakian, Milos, Sep 28

  26. Sivers effect: sea contributions GRV98, DSS FF M. Anselmino et al arXiv:0805.2677 GRV98, Kretzer FF S. Arnold et al arXiv:0805.2137 • Negative Kaons most sensitive to sea contributions. • Biggest uncertainty in experimental measurements (K- suppressed at large x). H. Avakian, Milos, Sep 28

  27. positivity bound Pretzelosity @ EIC 5x50 epX p- p+ • EIC measurement combined with CLAS12 will provide a complete kinematic range for pretzelosity measurements H. Avakian, Milos, Sep 28

  28. L polarization in the target fragmentation L polarization in TFR provides information on contribution of strange sea to proton spin (ud)-diquark is a spin and isospin singlet s-quark carries whole spin of L xF- momentum in the CM frame xF(L) Study polarized diquark fracture functions sensitive to the correlations between struck quark transverse momentum and the diquark spin. EIC CLAS12 Wide kinematical coverage of EIC would allow studies of hadronization in the target fragmentation region H. Avakian, Milos, Sep 28

  29. Hard Exclusive Processes and GPDs DVMP DVCS long. only hard vertices DVCS – for different polarizations of beam and target provide access to different combinations of GPDs H,H, E,E DVMP for different mesons is sensitive to flavor contributions (r0/r+/K* select H, E, for u/d flavors, p, h, K select H, E) H. Avakian, Milos, Sep 28

  30. Gluon Imaging with exclusive processes Goal: Transverse gluon imaging of nucleon over wide range of x: 0.001 < x < 0.1 Two-gluon exchange dominant for J/y, f, r production at large energies sensitive to gluon distribution squared! LO factorization ~ color dipole picture access to gluon spatial distribution in nuclei Fit with ds/dt = e-Bt • Measurements at DESY of diffractive channels (J/y, f, r, g) confirmed the applicability of QCD factorization: • t-slopes universal at high Q2 • flavor relations f:r A.Levy(hep:0907.2178) Hard exclusive processes provide access to transverse gluon imaging at EIC! H. Avakian, Milos, Sep 28

  31. p+ p+-p- CLAS12 p- EIC4x60 M(e’p+X) Quark Imaging with exclusive processes • V. Guzey, Ch. Weiss: Regge model • T. Horn: π+ empirical parameterization • More demanding in luminosity • Physics closely related to JLab 6/12 GeV • quark spin/flavor separations • nucleon/meson structure • Simulation for charged p+ production, assuming 100 days at a luminosity of 1034, with 5 on 50 GeV (s = 1000) Horn,Bruell,Weiss H. Avakian, Milos, Sep 28

  32. SSAs in exclusive pion production CLAS Dubna-2003 P.Kroll & S. Goloskokov arXiv:0906.0460 Transverse photon matters HERMES • HT SSAs are expected to be very significant • EIC can measure Q2 dependence of HT SSAs significantly extending the range of CLAS12 H. Avakian, Milos, Sep 28

  33. GPDs from cross section ratios M.Diehl et al. hep-ph/0506171 K*+ K+ • Study ratio observables: K/K*/r+,polarization transfer • Different final state mesons filter out different combinations of unpolarized (H,E) and polarized (H,E) GPDs. H. Avakian, Milos, Sep 28

  34. CLAS12 L S S* EIC4x60 detected Quark Imaging with exclusive processes Rate estimate for KΛ Horn,Cooper Need good resolution to identify exclusive events Using an empirical fit to kaon electroproduction data from DESY and JLab assuming 100 days at a luminosity of 1034, with 5 on 50 GeV (s = 1000) H. Avakian, Milos, Sep 28

  35. Chiral-odd GPDs with exclusive r,r+ Long distance part described by GPD HT hard • Large momentum • transfer, large rapidity gap • Virtual photon replaced with 2 gluons pT hard GPD Smaller rapidity gap r+ selects quark antiquark exchange with the nucleon Ivanov et al.Phys.Part.Nucl.35:S67-S70,2004 Enberg et al. Eur.Phys.J.C47:87-94,2006 Ratio of r0Lr+Tn/ r0Lr+Ln directly related to ratio of GPDs HT/H H. Avakian, Milos, Sep 28

  36. Summary • Studies of semi-inclusive and exclusive processes at EIC • Provide detailed info on gluon and sea quark spatial imaging of the nucleon • Measure transverse momentum distributions of partons at small x • Define quark-gluon correlations using the wide range of Q2 • Investigate hadronization in target fragmentation • EIC: Measurements related to the spin, spin orbit and quark-gluon correlations (HT) combined with JLab12 HERMES,COMPASS, RHIC,BELLE,BABAR,Fermilab,J-PARC,GSI data will help construct a more complete picture about the spin structure of the nucleon beyond the collinear approximation. Thank You! H. Avakian, Milos, Sep 28

  37. Support slides…. H. Avakian, Milos, Sep 28

  38. K/K* and L/S separations Detection of K+ crucial for separation of different final states (L,S,K*) H. Avakian, Milos, Sep 28

  39. hep-ph/9606390 Collins effect p+ leading pion out of page Simple string fragmentation for pions (Artru model) z L r production may produce an opposite sign AUT Leading r opposite to leading p(into page) z r L Fraction of direct kaons may be significantly higher than the fraction of direct pions. LUND-MC H. Avakian, Milos, Sep 28

  40. Collins Effect: from asymmetries to distributions need Combined analysis of Collins fragmentation asymmetries from proton and deuteron may provide independent to e+e- (BELLE) Information on the underlying Collins function. H. Avakian, Milos, Sep 28

  41. SIDIS kinematical plane and observables Target polarization Cross section is a function of scale variables x,y,z U unpolarized L long.polarized T trans.polarized z Beam polarization sin2f moment of the cross section for unpolarized beam and long. polarized target 41 H. Avakian, Milos, Sep 28

  42. Sivers effect in the target fragmentation A.Kotzinian High statistics of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region H. Avakian, Milos, Sep 28

  43. Transverse force on the polarized quarks Quark polarized in the x-direction with kT in the y-direction Force on the active quark right after scattering (t=0) Interpreting HT (quark-gluon-quark correlations) as force on the quarks (Burkardt hep-ph:0810.3589) 43 H. Avakian, Milos, Sep 28 JLab, Nov 25

  44. SSA with unpolarized target quark polarization 44 H. Avakian, Milos, Sep 28 JLab, Nov 25

  45. SSA with unpolarized target quark polarization 45 H. Avakian, Milos, Sep 28 JLab, Nov 25

  46. The Gluon Contribution to the Proton Spin Bruell,Ent Projected data on Dg/g with an EIC, via g + p  D0 + X K- + p+ assuming vertex separation of 100 mm. • Measure 90% of DG (@ Q2 = 10 GeV2) RHIC-Spin Open theoretical problem: At high Q2 one should resum the mass logarithms in g 1 . Since the signs of c(x, Q2) and Δc(x, Q2) are opposite, resummation can affect essentially predicted value ΔG/G ~ g 1 / F2 . RHIC-Spin N.Ya. Ivanov e.a., in preparation 46 H. Avakian, Milos, Sep 28 H. Avakian, Milos, Sep 28

  47. pQCD Predictions Resummation for R= FL/ FT Resummation for F2 For F2 the NLO and resummation contributions are very close CTEQ PDFs used for estimates • N.Ya.Ivanov, Nucl. Phys. B 814 (2009), 142 47 H. Avakian, Milos, Sep 28 H. Avakian, Milos, Sep 28

  48. Resummation for A= 2xFA/ F2 • L.N. Ananikyan, N.Ya. Ivanov,. Nucl.Phys.B762:256-283,2007. CTEQ PDFs used for estimates The mass logarithms resummation (or heavy-quark densities) should reduce the pQCD predictions for R= FL/ FT and A=2xFA/ F2. cos2f moment in charm meson production provides access to charm densities 48 H. Avakian, Milos, Sep 28 H. Avakian, Milos, Sep 28

  49. HERA Q2 27 GeV Q2 EIC ENC ENC EIC JLab (upgraded) compass JLab12 hermes JLab@6GeV Hard Scattering Processes: Kinematics Coverage collider experiments H1, ZEUS(EIC) 10-4<xB<0.02 (0.3):gluons (and quarks) in the proton fixed target experiments COMPASS, HERMES  0.006/0.02<xB<0.3 : gluons/valence and sea quarks JLab/JLab@12GeV  0.1<xB<0.7: valence quarks Study of high x domain requires high luminosity, low x higher energies H. Avakian, Milos, Sep 28

  50. HERA 27 GeV Q2 EIC ENC ENC JLab (upgraded) compass hermes JLab@6GeV Hard Scattering Processes: Kinematics Coverage collider experiments H1, ZEUS(EIC) 10-4<xB<0.02 (0.3):gluons (and quarks) in the proton fixed target experiments COMPASS, HERMES  0.006/0.02<xB<0.3 : gluons/valence and sea quarks JLab/JLab@12GeV  0.1<xB<0.7: valence quarks Q2 EIC(4x60) ENC(3x15) JLab12 Study of high x domain requires high luminosity, low x higher energies H. Avakian, Milos, Sep 28

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