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Polarized Drell-Yan Experiment at J-PARC

Polarized Drell-Yan Experiment at J-PARC. J-PARC Meeting for Spin and Hadron Physics Nishina Hall at RIKEN April 7 th , 2008 Yuji Goto (RIKEN/RBRC). J-PARC proposals. P04: measurement of high-mass dimuon production at the 50-GeV proton synchrotron

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Polarized Drell-Yan Experiment at J-PARC

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  1. Polarized Drell-Yan Experimentat J-PARC J-PARC Meeting for Spin and Hadron Physics Nishina Hall at RIKEN April 7th, 2008 Yuji Goto (RIKEN/RBRC)

  2. J-PARC 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 • to be submitted

  3. Origin of the nucleon spin 1/2 ? • EMC experiment at CERN • total quark spin constitutes a small fraction of the nucleon spin • integration in x = 0 ~ 1 makes uncertainty • more data to cover wider x region with more precise data necessary • SLAC/CERN/DESY/JLAB experiments • Gluon spin contribution ? • scaling violation in polarized DIS • success of the evolution equation of the perturbative QCD • limited sensitivity due to a limited range of Q2 • semi-inclusive polarized DIS • polarized hadron collision • Orbital angular momentum ? J. Ashman et al., NPB 328, 1 (1989). “proton spin crisis” longitudinally polarized measurements transversely polarized measurements

  4. Gluon spin contribution • ALL in neutral pion production • mid-rapidity at RHIC, s = 200 GeV G = 0.4 at Q2=1(GeV/c)2 G = 0.1 at Q2=1(GeV/c)2 gg + qg dominant sensitive to the gluon reaction GRSV-std scenario, G = 0.4 at Q2= 1(GeV/c)2, excluded by data on more than 3-sigma level

  5. Flavor-sorted quark polarization • Weak boson production • RHIC spin • s = 500 GeV • 2009 – • parity-violating asymmetry AL • reduction of uncertainties to determine the quak spin contribution  and gluon spin contribution G to the proton spin

  6. +  K p Transverse single-spin asymmetry (SSA) • Link to orbital angular momentum in the nucleon • forward rapidity • Fermilab E704, s = 20 GeV • RHIC, s = 200 GeV explained by many undetermined distribution and fragmentation functions: transversity, Sivers function, Collins function

  7. Drell-Yan experiment • The simplest process in hadron-hadron reactions • no QCD final-state effect • no polarized Drell-Yan experiment done yet • flavor asymmetry of the sea-quark distributions • unpolarized and longitudinally-polarized measurements • orbital angular momentum in the nucleon • Sivers effect (no Collins effect) • transversity distribution function, etc. • Why at J-PARC ? • polarized beam feasible in discussions with J-PARC and BNL accelerator physicists • high intensity/luminosity for small Drell-Yan cross section DIS Drell-Yan

  8. Flavor asymmetry of sea-quark distribution • Fermilab E866 • Possible origins • meson-cloud model • virtual meson-baryon state • chiral quark model • instanton model • chiral quark soliton model

  9. + is the origin of -quark excess in the proton? Flavor asymmetry of sea-quark distribution

  10. 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 vertically 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

  11. GS-C GS-A GRSV chiral quark soliton model prediction Polarized Drell-Yan experiment at J-PARC • Longitudinally-polarized measurement • ALL measurement • flavor asymmetry of sea-quark polarization 120-day run 75% polarization for a 51011 protons/spill polarized solid NH3 target, 75% hydrogen polarization and 0.15 dilution factor

  12. GS-C GS-A GRSV Flavor asymmetry of sea-quark polarization • Polarized Drell-Yan experiment at J-PARC • x = 0.25 – 0.5 • W production at RHIC • x = 0.05 – 0.1 reduction of uncertainties to determine the quak spin contribution  and gluon spin contribution G to the proton spin

  13. Polarized Drell-Yan experiment at J-PARC • Orbital angular momentum • in hadron-hadron reaction, no direct link between measurement and theory (yet) • but, any partonic transverse motion and correlation should be related • Sivers effect / higher-twist effect • SSA (AN) measurement • Sivers effect and higher-twist effect provide the same description of SSA on Drell-Yan and semi-inclusive DIS at moderate qT: QCD << qT << Q • Sivers function in Drell-Yan should have a sign opposite to that in DIS • sensitive QCD test between e+p data and p+p data 4 < M+- < 5 GeV integrated over qT 1000 fb-1 (120-day run), 75% polarization, no dilution factor Theory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data

  14. Polarized Drell-Yan experiment at J-PARC • ATT measurement • h1(x): transversity • remaining leading-order distribution function of the nucleon • SSA measurement, sin(+S) term • h1(x): transversity • h1(1)(x): Boer-Mulders function (1st moment of)

  15. Unpolarized Drell-Yan experiment at J-PARC • Boer-Mulders function h1(x, kT2) • angular distribution of unpolarized Drell-Yan • Lam-Tung relation reflect the spin-1/2 nature of quarks • violation of the Lam-Tung relation suggests non-perturbative origin • correlation between transverse quark spin and quark transverse momentum 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

  16. Experimental condition study • Previous simulation study which made the figure below was wrong • target position was fixed at z = 0 (at the edge of the first magnet) • correctly, this should be z = -1800 cm ~ -1300 cm (50 cm target) • yield should be ~5 times smaller • but, higher beam intensity is possible for unpolarized liq.H2 target • 10 times higher possible? 51012 ppp = 11012 /sec ? PYTHIA simulation: mass = 4 – 5 GeV/c2 beam intensity: 51011 ppp = 11011 /sec 120 day = 107 sec beam on target: 51017 (with 50% duty factor) number density of liq.H2 target: 0.429x1023 /cm3 luminosity = botnumber densitytarget length = 1000 fb-1 1000 fb-1 (120-day run), 75% polarization, no dilution factor Theory calculation by Ji, Qiu, Vogelsang and Yuan based on Sivers function fit of HERMES data

  17. Experimental condition study • J-PARC experiment should be optimized for 4 GeV/c2 virtual photon • PYTHIA simulation: mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4 • each of magnet/detector geometry same as E906, but total apparatus length 60% shorter

  18. Experimental condition study • E906 optimized for 7 GeV/c2 virtual photon • PYTHIA simulation mass = 7 – 7.1 GeV/c2, xF = 0.2 – 0.4 mass = 4 – 4.1 GeV/c2, xF = 0.2 – 0.4

  19. Experimental condition study • Smaller boost • wider aperture of the first magnet necessary • Sivers effect measurement • single beam-spin asymmetry • maybe easier to use nuclear targets • More studies • absorber & beam target thickness, etc. • trigger rate and resolution

  20. pQCD studies by Yokoya-san, et al. • NLO/NNLO

  21. pQCD studies by Yokoya-san, et al. • Scheme dependence

  22. pQCD studies by Yokoya-san, et al.

  23. pQCD studies by Yokoya-san, et al.

  24. pQCD studies by Yokoya-san, et al.

  25. pQCD studies by Yokoya-san, et al.

  26. pQCD studies by Yokoya-san, et al.

  27. pQCD studies by Yokoya-san, et al.

  28. pQCD studies by Yokoya-san, et al. • s = 62 GeV

  29. pQCD studies by Yokoya-san, et al. • s = 10 GeV

  30. pQCD studies by Yokoya-san, et al.

  31. pQCD studies by Kawamura-san, et al.

  32. pQCD studies by Kawamura-san, et al.

  33. Summary • Polarized Drell-Yan experiment with dimuon measurment using polarized proton beam at J-PARC has a rich physics programs • flavor asymmetry of sea-quark polarization  higher precision for  and G • SSA measurements for Sivers and higher-twist effects and transversity  link to orbital-angular momentum • We propose to make the J-PARC facility allow acceleration of polarized proton beams to 30-50 GeV • feasible in discussion with J-PARC and BNL accelerator physicists • technically, there is no showstopper • Theoretical studies at J-PARC energy has progressed • showing convergence to compare with experimental data • More studies for experimental condition to be done • for the next proposal

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