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Drell-Yan with Fixed Target at RHIC

Drell-Yan with Fixed Target at RHIC. “RHIC Spin: The Next Decade” at Iowa State University May 15 th , 2010 Yuji Goto (RIKEN/RBRC). Drell-Yan experiment. The simplest process in hadron-hadron reactions No QCD final state effect Fermilab E866 Flavor asymmetry of sea-quark distribution.

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Drell-Yan with Fixed Target at RHIC

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  1. Drell-Yan with Fixed Targetat RHIC “RHIC Spin: The Next Decade” at Iowa State University May 15th, 2010 Yuji Goto (RIKEN/RBRC)

  2. Drell-Yan experiment • The simplest process in hadron-hadron reactions • No QCD final state effect • Fermilab E866 • Flavor asymmetry of sea-quark distribution DIS Drell-Yan

  3. Drell-Yan experiment • Flavor asymmetry of sea-quark distribution • Possible origins • meson-cloud model • virtual meson-baryon state • chiral quark model • instanton model • chiral quark soliton model • + in the proton as an origin of anti-d quark • pseudo-scaler meson should have orbital angular momentum in the proton… • Polarized Drell-Yan experiment • Not yet done! • 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.

  4. Single transverse-spin asymmetry • Sivers effect • Correlation between nucleon transverse spin and parton transverse momentum (Sivers distribution function) • Related to the orbital angular momentum in the proton (and the shape of the proton) • Multi-dimensional structure of the proton • Initial-state or final-state interaction with remnant partons J-PARC 50-GeV polarized beam s ~ 10 GeV RHIC collider s = 200 GeV Anselmino, et al., PRD79, 054010 (2009)

  5. Sivers function measurement Sign of Sivers function determined by single transverse-spin (SSA) measurement of DIS and Drell-Yan processes Should be opposite each other Initial-state interaction or final-state interaction with remnant partons < 1% level multi-points measurements have already beendone for SSA of DIS process x = 0.005 – 0.3 (more sensitive in lower-x region) comparable level measurement needs to be done for SSA of Drell-Yan process for comparison

  6. J-PARC and/or RHIC • J-PARC • Advantage • High intensity = high luminosity • Disadvantage • Smaller cross section (at the same invariant mass) • Uncertainties • Availability of 50 GeV beam • Polarized proton beam? • RHIC • Advantage • Polarized proton beam available • Larger cross section (at the same invariant mass) • Disadvantage • Luminosity? • Collider or fixed-target (internal-target) experiment

  7. FNAL-E906 dimuon spectrometer Station 2 and 3: Hodoscope array Drift Chamber tracking Hadron Absorber Station 1: Hodoscope array MWPC tracking Solid Iron Focusing Magnet, Hadron absorber and beam dump Mom. Meas. (KTeV Magnet) Station 4: Hodoscope array Prop tube tracking 4.9m 25m Liquid H2, d2, and solid targets

  8. PYTHIA simulation with IP2 configuration IP2 configuration shown in the next slide detector components from FNAL-E906 apparatus E906: total z-length ~25 m IP2: available z-lengh ~14 m z-length of FMAG (1st magnet) is shortened because of limited z-length at IP2 PYTHIA simulation s = 22 GeV (Elab = 250 GeV) luminosity assumption 10,000 pb-1  10 times larger luminosity necessary than collider experiments because of ~10 times smaller cross section  acceptance (in the same mass region) M = 4.5  8 GeV acceptance for Drell-Yan dimuon signal is studied momentum resolution (geometric) 6  10-4  p (GeV/c) background rate needs to be studied

  9. IP2 (overplotted on BRAHMS) Internal target position St.4 MuID St.1 St.2 St.3 FMAG 3.9 m Mom.kick 2.1 GeV/c KMAG 2.4 m Mom.kick 0.55 GeV/c 14 m 18 m

  10. Drell-Yan at IP2 rapidity E1 vs E2 (accepted events) all generated dumuon from Drell-Yan passed through FMAG passed through St. 1 passed through St. 2 passed through St. 3 accepted by all detectors • E1, E2: energy of dimuons • energy cut shown ~10 GeV

  11. Drell-Yan at IP2 rapidity xF accepted 4.5 - 8 GeV/c2 4.5 - 5 GeV/c2 5 - 6 GeV/c2 6 - 8 GeV/c2 pT x1

  12. Drell-Yan at IP2 About 50,000 events for 10,000 pb-1 x1 vs x2 (accepted events) x1: x of beam proton (polarized) x2: x of target proton

  13. Collider vs fixed-target • x1 & x2 coverage • Collider experiment with PHENIX muon arm (simple PYTHIA simulation) • s = 500 GeV • Angle & E cut only • 1.2 < || < 2.2 (0.22 < || < 0.59), E > 2, 5, 10 GeV • (no magnetic field, no detector acceptance) • luminosity assumption 1,000 pb-1 • M = 4.5  8 GeV • Single arm: x1 = 0.05 – 0.1 (x2 = 0.001 – 0.002) • Very sensitive x-region of SIDIS data • Fixed-target experiment • x1 = 0.25 – 0.4 (x2 = 0.1 – 0.2) • Can explore higher-x region with better sensitivity PHENIX muon arm (angle & E cut only) Fixed-target experiment x2 x2 x1 x1

  14. Fixed-target experiment Phase-1: parasitic experiment (with other collider experiments) Beam intensity 2×1011×10MHz = 21018/sec Cluster or pellet target 1015/cm2 50 times thinner than RHIC CNI carbon target Luminosity 2×1033/cm2/sec 10,000pb-1 with 5×106sec 8 weeks, or 3 years (10 weeks×3) with efficiency and live time Reaction rate 2×1033×50mb = 108/sec = 100MHz Beam lifetime 2×1011×100bunch / 108 = 2×105sec (at longest) More factor to make the lifetime shorter, but expected to be still long enough

  15. Fixed-target experiment • Phase-2: dedicated experiment • Beam intensity 2×1011×30MHz = 6×1018/sec • Cluster, pellet or solid target 1016/cm2 • 5 times thinner than RHIC CNI carbon target • Luminosity 6×1034/cm2/sec • 10,000pb-1 with 2×105sec • 3 days, or 2 weeks with efficiency and live time • Or 50,000pb-1 with 106sec • 2 weeks, or 8 weeks with efficiency and live time • Reaction rate 6×1034×50mb = 3×109/sec = 3GHz • Beam lifetime 2×1011×300bunch / 3×109 = 2×104sec ~ 6hours • More factor to make the lifetime shorter • Special short-interval operation necessary

  16. Physics • Experimental sensitivity • Phase-1 (parasitic operation) • L = 2×1033 cm-2s-1 • 10,000 pb-1 with 5106 s ~ 8 weeks (1 year), or 3 years of beam time by considering efficiency and live time • Phase-2 (dedicated operation) • L = 6×1034 cm-2s-1 • 50,000 pb-1 with 106 s ~ 2 weeks, or 8 weeks (1 year) 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) 10,000 pb-1 (phase-1) 50,000 pb-1 (phase-2)

  17. pQCD studies of Drell-Yan cross section pQCD correction can be controlled NNLO calculation Hamberg, van Neerven, Matsuura, Harlander, Kilgore NLL, NNLL calculation Yokoya, et al... by Hiroshi Yokoya

  18. Letter of Intent • Author list • ANL • D. F. Geesaman, R. E. Reimer, J. Rubin • UIUC • M. Grosse Perdekamp, J.-C. Peng • KEK • N. Saito, S. Sawada • LANL • M. Brooks, X. Jiang, G. Kunde, M. J. Leitch, M. X. Liu, P. L. McGaughey • RIKEN • Y. Fukao, Y. Goto, I. Nakagawa, R. Seidl, A. Taketani • RBRC • K. Okada • Stony Brook Univ. • A. Deshpande • Tokyo Tech • K. Nakano, T.-A. Shibata • Yamagata Univ. • N. Doshita, T. Iwata, K. Kondo, Y. Miyachi

  19. Fixed-target experiment Internal target Storage cell target (polarized) H2, D2, 3He 1014 / cm2 HERMES Cluster jet target H2, D2, N2, CH4, Ne, Ar, Kr, Xe, … 1014 – 1015 / cm2 CELSIUS (Uppsala), FNAL-E835, Muenster, COSY, GSI, … Pellet target H2, D2, N2, Ne, Ar, Kr, Xe, … 1015 – 1016 / cm2 CELSIUS (Uppsala), COSY, GSI, … Double-spin experiment possible Low density = low luminosity Issue to be used in the RHIC ring High luminosity Only single-spin experiment possible

  20. Cost and schedule • To be considered… • Cost • Accelerator & experimental hall (IP2) • the most expensive part? • Internal target • e.g. PANDA pellet target: $1.5M R&D, infrastructure + $1.5M construction • Experimental apparatus • FNAL-E906 magnet (modification) or other existing magnet at BNL • FNAL-E906 apparatus (modification) and/or new/existing apparatus • Schedule • 2010-2013 FNAL-E906 beam time • 2011-13 accelerator R&D, internal target R&D + construction • 2014 experimental setup & commissioning at RHIC • 2015-2017 phase-1: parasitic experiment • 2018 phase-2: dedicated experiment

  21. Issues (as a summary) • Requirement for target thickness • In phase-1 (parasitic operation), 1015 /cm2 thickness is necessary to achieve L = 21033 cm-2s-1 • Pellet target (~1015 /cm2) or cluster-jet target (up to 81014/cm2 ?) is necessary • If it is not achieved, the internal-target experiment would not be competitive against collider experiments • In collider experiments, L = 2(or 3)1032 is expected and cross section ( acceptance) is >10 times larger • In phase-2 (dedicated operation), 10-times larger thickness, 1016 /cm2 is expected • Requirement for accelerator • Compensation of dipole magnets in the experimental apparatus • both beams need to be restored on axis in two colliding-beam operation • Size of the experimental site and possible target-position (with proper beam operation) • Reaction rate (peak rate) and beam lifetime • Radiation issues • Beam loss/dump requirement

  22. Backup slides

  23. Polarized Drell-Yan experiment • Single transverse-spin asymmetry • Sivers function measurement • Transversity  Boer-Mulders function • Double transverse-spin asymmetry • Transversity (quark  antiquark for p+p collisions) • Double helicity asymmtry • Flavor asymmetry of quark polarization • Other physics • Parity violation asymmetry?

  24. Sivers function measurement Sign of Sivers function determined by single transverse-spin (SSA) measurement of DIS and Drell-Yan processes Should be opposite each other Initial-state interaction or final-state interaction with remnant partons Test of TMD factorization Explanation by Vogelsang and Yuan… From “Transverse-Spin Drell-Yan Physics at RHIC,” Les Bland, et al., May 1, 2007 DIS Drell-Yan “toy” QED attractive repulsive QCD

  25. Single transverse-spin asymmetry • Sivers function measurement • Transversity  Boer-Mulders function measurement by Stefano Melis

  26. Polarized and unpolarized Drell-Yan experiment • ATT measurement • h1(x): transversity • quark  antiquark in p+p collisions • Unpolarized measurement • angular distribution of unpolarized Drell-Yan • Boer-Mulders function • 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

  27. Polarized Drell-Yan experiment • Longitudinally-polarized measurement • ALL measurement • flavor asymmetry of sea-quark polarization • SIDIS data from HERMES, and new COMPASS 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 Bhalerao, statistical model Cao & Signa, bag model Cao & Signa, meson cloud Wakamatsu, CQSM SU(2) Wakamatsu, CQSM SU(3) HERMES, PRD71: 012003, 2005

  28. 4.9m FNAL-E906 dimuon spectrometer Station 2 and 3: Hodoscope array Drift Chamber tracking Hadron Absorber Station 1: Hodoscope array MWPC tracking Solid Iron Focusing Magnet, Hadron absorber and beam dump Mom. Meas. (KTeV Magnet) Station 4: Hodoscope array Prop tube tracking 25m Solid iron magnet • Reuse SM3 magnet coils • Sufficient Field with reasonable coils (amp-turns) • Beam dumped within magnet Liquid H2, d2, and solid targets

  29. 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... by Hiroshi Yokoya

  30. Collider experiment • Very simple PYTHIA simulation for PHENIX muon arm • s = 500 GeV • Angle & E cut only • 1.2 < || < 2.2 (0.22 < || < 0.59) • E > 2, 5, 10 GeV • (no magnetic field, no detector acceptance) • RHIC-II luminosity assumption 1,000 pb-1 • M = 4.5  8 GeV 110K events total with 2-GeV cut

  31. Collider experiment • “Transverse-Spin Drell-Yan Physics at RHIC” • Les Bland, et al., May 1, 2007 • s = 200 GeV • PHENIX muon arm • STAR FMS (Forward Muon Spectrometer) • Large background from b-quark • s = 500 GeV may be better… • Higher luminosity and larger cross section

  32. Collider experiment • Very simple PYTHIA simulation for a dedicated collider experiment • s = 500 GeV • Angle & E cut only • || < 2.2 • E > 2, 5, 10 GeV • (no magnetic field, no detector acceptance) • RHIC-II luminosity assumption 1,000 pb-1 • M = 4.5  8 GeV 550K events total with 2-GeV cut

  33. Fixed-target experiment • Simple PYTHIA simulation for a fixed target experiement • s = 22 GeV (Elab = 250 GeV) • Angle & E cut only • 0.03 <  < 0.1 • E > 2, 5, 10 GeV • (no magnetic field, no detector acceptance) • luminosity assumption 10,000 pb-1 •  10 times larger luminosity necessary than collider experiments • because of ~10 times smaller cross section  acceptance • M = 4.5  8 GeV Red: E > 2 GeV cut Green: E > 5 GeV cut Blue: E > 10 GeV cut 35K events total with 10-GeV cut

  34. FNAL-E906 First Magnet (FMag)

  35. FNAL-E906 First Magnet (FMag)

  36. FNAL-E906 Second Magnet (KMag)

  37. Accelerator issues • Experimental dipole magnets • Beam axis restoration (one beam on target, the other beam displaced) • Size of the experimental site and possible target-position (with proper beam operation) • IP2 (BRAHMS) area? • Reaction rate (peak rate) and beam lifetime • Radiation issues • Beam loss/dump requirement

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