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偏極 Drell-Yan 実験による 核子構造の多次元的理解に向けて

偏極 Drell-Yan 実験による 核子構造の多次元的理解に向けて. 「核子構造研究の新展開 2011 」 @KEK 2011 年 1 月 8 日 ( 土 ) 後藤雄二（理研）. Outline of this talk. Introduction Transverse structure of the proton Drell-Yan measurement Polarized Drell-Yan experiments COMPASS GSI Fermilab RHIC J-PARC Summary. 2. Introduction.

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偏極 Drell-Yan 実験による 核子構造の多次元的理解に向けて

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  1. 偏極Drell-Yan実験による核子構造の多次元的理解に向けて偏極Drell-Yan実験による核子構造の多次元的理解に向けて 「核子構造研究の新展開2011」@KEK 2011年1月8日(土) 後藤雄二（理研）

  2. Outline of this talk • Introduction • Transverse structure of the proton • Drell-Yan measurement • Polarized Drell-Yan experiments • COMPASS • GSI • Fermilab • RHIC • J-PARC • Summary 2

  3. Introduction • Transverse-spin asymmetry measurement • Theoretical development to understand the transverse structure of the nucleon • Sivers effect, Collins effect, higher-twist effect, … • Relation to orbital angular momentum inside the nucleon FNAL-E704 s = 20 GeV RHIC-STAR s = 200 GeV 3

  4. Introduction • Transverse-spin asymmetry • Sivers effect (Sivers function) • Transverse-momentum dependent (TMD) distribution function • Collins effect (transversity & Collins fragmentation function) • higher-twist effect • … • Drell-Yan process • to distinguish Sivers effect • to separate initial-state and final-state interaction with remnant partons • Comparison with semi-inclusive DIS results

  5. Introduction • Transverse structure of the proton • Transversity distribution function • Correlation between nucleon transverse spin and parton transverse spin • TMD distribution functions • Sivers function • Correlation between nucleon transverse spin and parton transverse momentum (kT) • Boer-Mulders function • Correlation between parton transverse spin and parton transverse momentum (kT) Leading-twist transverse momentum dependent (TMD) distribution functions 5

  6. Sivers function M. Anselmino, et al. EPJA 39, 89 (2009) • Single-spin asymmetry (SSA) measurement • < 1% level multi-points measurements have been done for SSA of DIS process • Valence quark region: x = 0.005 – 0.3 • (more sensitive in lower-x region) Sivers function u-quark d-quark 6

  7. Polarized Drell-Yan • Many new inputs for remaining proton-spin puzzle • flavor asymmetry of the sea-quark polarization • transversity distribution • transverse-momentum dependent (TMD) distributions • Sivers function, Boer-Mulders function, etc. • “Non-universality” of Sivers function • Sign of Sivers function determined by SSA measurement of DIS and Drell-Yan processes should be opposite each other • final-state interaction with remnant partons in DIS process • Initial-state interaction with remnant partons in Drell-Yan process • Fundamental QCD prediction • One of the next milestones for the field of hadron physics

  8. Goal of the experiment • Comparison with DIS data • DIS data • < 1% level multi-points measurements have already been done for SSA of DIS process • 0.005 < x < 0.3 • Comparable level measurement needs to be done for SSA of Drell-Yan process for comparison • Measure not only the sign ofthe Sivers function but also the shape of the function • x region • Valence quark region: x ~ 0.2 • Expect to show the largest asymmetry • … and explore larger x region M. Anselmino, et al. EPJA 39, 89 (2009) Sivers function u-quark d-quark 8

  9. Boer-Mulders function • Single transverse-spin asymmetry • Transversity  Boer-Mulders function measurement • Distinguished from Sibers function measurement by different angular distribution • Unpolarized measurement • Angular distribution • Violation of the Lam-Tung relation With Boer-Mulders function h1┴: ν(π-Wµ+µ-X)~valence h1┴(π)*valence h1┴(p) ν(pdµ+µ-X)~valence h1┴(p)*sea h1┴(p) L.Y. Zhu,J.C. Peng, P. Reimer et al. hep-ex/0609005 9

  10. Double-spin asymmetries • Double transverse-spin asymmetry • transversity • quarkantiquark for p+p collisions • Double helicity asymmetry • flavor asymmetry of sea-quark polarization • SIDIS data from HERMES and COMPASS preliminary data available • W data from RHIC will be available in the near future • Polarized Drell-Yan data will be able to cover higher-x region 10

  11. Future polarized Drell-Yan experiments 11

  12. Drell-Yan experiment Momentum analysis • Fermilab E966/SeaQuest • Dimuon spectrometer • Main injector beam Ebeam = 120 GeV • Higher-x region: x = 0.1 – 0.45 • Beam time: 2010 – 2013 Focusing magnet Hadron absorber Beam dump 23

  13. Polarized Drell-Yan experiments at RHIC • “Transverse-Spin Drell-Yan Physics at RHIC” • http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf • Les Bland, et al., May 1, 2007 • s = 200 GeV • PHENIX muon arm • STAR FMS (Forward Muon Spectrometer) • Discussions at PHENIX and STAR underway in their decadal plan discussion with their upgrade plan • Two new Letter-of-Intent submitted to BNL PAC • Collider experiment dedicated to the polarized Drell-Yan experiment • “Feasibility Test of Large Rapidity Drell-Yan Production at RHIC” • Fixed-target experiment • “Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC” 30

  14. Collider experiment LoI • http://www.bnl.gov/npp/docs/pac0610/Crawford_LoI.100524.v1.pdf 31

  15. Collider experiment LoI 32

  16. Fixed-target experiment LoI • Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC • http://www.bnl.gov/npp/docs/pac0610/Goto_rhic-drell-yan.pdf • Academia Sinica (Taiwan): W.C. Chang • ANL (USA): D.F. Geesaman, P.E. Reimer, J. Rubin • UC Riverside (USA): K.N. Barish • UIUC (USA): M. Groose Perdekamp, J.-C. Peng • KEK (Japan): N. Saito, S. Sawada • LANL (USA): M.L. Brooks, X. Jiang, G.L. Kunde, M.J. Leitch, M.X. Liu, P.L. McGaughey • RIKEN/RBRC (Japan/USA): Y. Fukao, Y. Goto, I. Nakagawa, K. Okada, R. Seidl, A. Taketani • Seoul National Univ. (Korea): K. Tanida • Stony Brook Univ. (USA): A. Deshpande • Tokyo Tech. (Japan): K. Nakano, T.-A. Shibata • Yamagata Univ. (Japan): N. Doshita, T. Iwata, K. Kondo, Y. Miyachi 33

  17. IP2 (overplotted on BRAHMS) Internal target position St.4 MuID St.1 St.2 St.3 F MAG3.9 m Mom.kick 2.1 GeV/c KMAG 2.4 m Mom.kick 0.55 GeV/c 14 m 18 m 34

  18. Experimental sensitivities • PYTHIA simulation • s = 22 GeV (Elab = 250 GeV) • luminosity assumption 10,000 pb-1 • Phase-1 (parasitic operation)10,000 pb-1 • Phase-2 (dedicated operation)30,000 pb-1 • 4.5 GeV < M < 8 GeV • acceptance for Drell-Yan dimuon signal is studied all generated dumuon from Drell-Yan accepted by all detectors 35

  19. Experimental sensitivities • About 50K events for 10,000pb-1 luminosity • x-coverage: 0.2 < x < 0.5 • x1: x of beam proton (polarized) • x2: x of target proton 36

  20. Experimental sensitivities • Phase-1 (parasitic operation) • L = 2×1033 cm-2s-1 • 10,000 pb-1 with 5×106 s ~ 8 weeks, or 3 years (10 weeks×3) of beam time by considering efficiency and live time • Phase-2 (dedicated operation) • L = 3×1034 cm-2s-1 • 30,000 pb-1 with 106 s ~ 2 weeks, or 8 weeks of beam time by considering efficiency and live time Theory calculation: U. D’Alesio and S. Melis, private communication; M. Anselmino, et al., Phys. Rev. D79, 054010 (2009) Measure not only the sign ofthe Sivers function but also the shape of the funcion 10,000 pb-1 (phase-1) 40,000 pb-1 (phase-1 + phase-2) 37

  21. J-PARC Drell-Yan proposals P04: measurement of high-mass dimuon production at the 50-GeV proton synchrotron spokespersons: Jen-Chieh Peng (UIUC) and Shinya Sawadas (KEK) collaboration: Abilene Christian Univ., ANL, Duke Univ., KEK, UIUC, LANL, Pusan National Univ., RIKEN, Seoul National Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ. including polarized physics program, but not discussed “deferred” P24: polarized proton acceleration at J-PARC contact persons: Yuji Goto (RIKEN) and Hikaru Sato (KEK) collaboration: ANL, BNL, UIUC, KEK, Kyoto Univ., LANL, RCNP, RIKEN, RBRC, Rikkyo Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ. polarized Drell-Yan included as a physics case “no decision” Next proposal for the polarized physics program not yet submitted

  22. Dimuon experiment at J-PARC (P04) based on the Fermilab spectrometer for 800 GeV length to be reduced but the aperture to be increased two bending magnets with pT kick of 2.5 GeV/c and 0.5 GeV/c tracking by three stations of MWPC and drift chambers muon id and tracking tapered copper beam dump and Cu/C absorbers placed within the first magnet

  23. Polarized Drell-Yan experiment at J-PARC analyzing magnet 51cm 127cm polarized beam red liquid H2 target blue nuclear target 4 < M+- < 5 GeV integrated over qT • Single transverse-spin asymmetry • Sivers effect measurement • Experimental condition • higher beam intensity is possible for unpolarized liquid H2 target, or nuclear target • 51012 ppp = 2.510122sec in 1pulse (5sec) possible? • PYTHIA simulation • 75% polarization beam • 120 days, beam on target 51017 (with 50% duty factor) • ~5% liquid H2 target • 10000 fb-1 luminosity • ~20% nuclear target • 40000 fb-1 luminosity • mass 4 – 5 GeV/c2 40 40

  24. pQCD studies of Drell-Yan cross section pQCD correction can be controlled at J-PARC energy NNLO calculation Hamberg, van Neerven, Matsuura, Harlander, Kilgore NLL, NNLL calculation Yokoya, et al...

  25. Polarized proton acceleration (P24) Polarized beam feasible in discussions with J-PARC and BNL accelerator physicists How to keep the polarization given by the polarized proton source depolarizing resonance imperfection resonance magnet errors and misalignments intrinsic resonance vertical focusing field weaken the resonance fast tune jump harmonic orbit correction intensify the resonance and flip the spin rf dipole snake magnet How to monitor the polarization polarimeters

  26. Polarized proton acceleration at AGS/RHIC Proposed scheme for the polarized proton acceleration at J-PARC is based on the successful experience of accelerating polarized protons to 25 GeV at BNL AGS BRAHMS & PP2PP PHOBOS Absolute Polarimeter (H jet) RHIC pC Polarimeters PHENIX Full Helical Siberian Snakes STAR Spin Rotators Spin Rotators Pol. H- Source LINAC BOOSTER Partial Solenoidal Snake rf Dipole AGS Warm Partial Helical Siberian Snake 200 MeV Polarimeter AGS Internal Polarimeter AGS pC Polarimeters Cold Partial Helical Siberian Snake

  27. Polarized proton acceleration at J-PARC pC CNI Polarimeter Extracted Beam Polarimeter Pol. H- Source rf Dipole 30% Partial Helical Siberian Snakes 180/400 MeV Polarimeter BRAHMS & PP2PP PHOBOS Absolute Polarimeter (H jet) RHIC pC Polarimeters PHENIX STAR Pol. H- Source LINAC BOOSTER rf Dipole AGS Warm Partial Helical Siberian Snake 200 MeV Polarimeter AGS Internal Polarimeter AGS pC Polarimeters Cold Partial Helical Siberian Snake

  28. Accelerating polarized protons in the MR AGS 25% superconducting helical snake helical dipole coil correction solenoid and dipoles measured twist angle 2 deg/cm in the middle ~4 deg/cm at ends

  29. Accelerating polarized protons in the MR Possible location of partial helical snake magnets in the MR First 30% snake Second 30% snake

  30. Summary • Polarized Drell-Yan measurement • The simplest process in hadron-hadron reaction • But, not yet done because of technical difficulties so far • Sivers function measurement in the valence-quark region from the SSA of Drell-Yan process • Test of the QCD prediction “Sivers function in the Drell-Yan process has an opposite sign to that in the DIS process” • Milestone for the field of hadron physics • Several proposed (some approved and not-yet-proposed) experiments • COMPASS/GSI/Fermilab/RHIC/J-PARC/… • In this decade • Measurement not only the sign of the Sivers function, but also the shape of the function feasible 47

  31. Backup slides

  32. RHIC/PHENIX in the future • PHENIX upgrades • Muon trigger • Silicon VTX • More upgrades discussed in the decadal plan • RHIC upgrades • Electron lens & 56 MHz storage RF • EIC (Electron Ion Collider) • 2020 ? • Spin physics • 2009-2014(?) W measurement • Helicity structure of the proton • Quark-spin contribution • Gluon-spin contribution • Transverse structure of the proton • Orbital angular momentum • Drell-Yan measurement from PHENIX decadal plan 49

  33. Introduction • Origin of the proton spin 1/2 - “proton-spin puzzle” • Polarized DIS experiments • Polarized hadron collision experiments • Longitudinal-spin asymmetry measurement • Helicity structure of the proton • Quark-spin contribution • Gluon-spin contribution • Large restriction for the gluon-spin contribution or gluon helicity distribution Midrapidity jet at STAR Midrapidity 0 at PHENIX 50

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