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Spin Physics with Primary Beam at J-PARC

Spin Physics with Primary Beam at J-PARC. J-PARC Hadron Structure Workshop at KEK December 1 st , 2005 Yuji Goto (RIKEN/RBRC). Outline. Introduction Spin physics with polarized target Spin physics with polarized primary beam Spin physics with polarized beam & target Detector idea Summary.

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Spin Physics with Primary Beam at J-PARC

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  1. Spin Physics with Primary Beam at J-PARC J-PARC Hadron Structure Workshop at KEK December 1st, 2005 Yuji Goto (RIKEN/RBRC)

  2. Outline • Introduction • Spin physics with polarized target • Spin physics with polarized primary beam • Spin physics with polarized beam & target • Detector idea • Summary Yuji Goto (RIKEN/RBRC)

  3. Introduction • Origin of the nucleon spin 1/2 ? • polarized DIS experiments showed the quark-spin contribution is only 10-30% • gluon-spin contribution ? • orbital angular momentum ? • Scaling violation in polarized DIS B. Adeva et al., PRD 58, 112002 (1998). P.L. Anthony et al., PLB 493, 19 (2000). Yuji Goto (RIKEN/RBRC)

  4. lepton beam g*  or  heavy flavor gluon  or  nucleon target Introduction • Semi-inclusive DIS • high-pT hadron pairs • open charm production Yuji Goto (RIKEN/RBRC)

  5. proton beam  or  gluon photon  or  proton beam proton beam  or  gluon heavy flavor gluon  or  proton beam Introduction • Present target at RHIC – gluon-spin contribution • polarized hadron collision • leading-order gluon measurement K. Tanida’s presentation yesterday direct photon production heavy-flavor production Yuji Goto (RIKEN/RBRC)

  6. Introduction • Gluon contribution – PHENIX ALL of 0 • PHENIX official statement • conclusively excludes GRSV maximal scenario • consistent with GRSV standard and GRSV g=0 input scenarios • Personal statement • optimum g at input scale: somewhere g = 0 ~ 0.4 • 1-sigma region: g < 0.4 • orbital angular momentum measurements should be developed for the final solution GRSV-max: g = 1.84 GRSV-std: g = 0.42 at Q2=1(GeV/c)2 best fit to DIS data Yuji Goto (RIKEN/RBRC)

  7. STAR Introduction STAR collaboration, hep-ex/0310058, Phys. Rev. Lett. 92 (2004) 171801 • Orbital angular momentum • hint in hadron reactions • asymmetries in angular distribution of semi-inclusive hadron production at polarized DIS exps STAR at RHIC: s = 200 GeV Fermilab E704: Elab = 200 GeV Yuji Goto (RIKEN/RBRC)

  8. Introduction • Theory developments • Sivers effect • spin and kT correlation in initial state • related to orbital angular momentum inside the nucleon • Collins effect • transversity distribution function and spin-dependent fragmentation function • higher-twist effect • Qiu and Sterman (initial-state) / Koike (final-state) twist-3 pQCD calculations • (DVCS in lepton scattering exps. for orbital angular momentum measurement) • issues at J-PARC – applicability of pQCD M. Stratmann’s presentation Yuji Goto (RIKEN/RBRC)

  9. Spin physics with polarized target at J-PARC • Forward pions  backward AN (xF < 0) • sensitive to the gluon Sivers effect at fixed-target exp. energies • not very sensitive at collider energies Elab = 200 GeV s = 19.4 GeV RHIC: s = 200 GeV M. Anselmino, U. D’Alesio, F. Murgia, et al. Yuji Goto (RIKEN/RBRC)

  10. Spin physics with polarized target at J-PARC • Forward pions • start with simple forward spectrometer with some particle-ID detectors • EM calorimeter for0 • to be moved when measuring more forward region polarized target 1m EM calorimeter spectrometer + some particle-ID 1m 5m c.m. 90 degree ~ 0.19 radian Yuji Goto (RIKEN/RBRC)

  11. Spin physics with polarized primary beam • Forward pions  forward AN (xF > 0) • confirmation of E704 asymmetries at smaller energies • BNL-E925 at Elab = 22 GeV confirmed for charged pions • pT dependence will give more information • D-meson • gluon fusion or quark-pair annihilation • no single-spin transfer to the final state • sensitive to initial state effect: Sivers effect • to be measured at RHIC: PHENIX with silicon upgrade (2009) Yuji Goto (RIKEN/RBRC)

  12. Spin physics with polarized primary beam • D-meson • collider energies: gluon-fusion dominant • sensitive to gluon Sivers effect • fixed-target energies: quark-pair annihilation dominant • sinsitive to quark Sivers effect • complementary J-PARC: Elab = 50 GeV RHIC: s = 200 GeV M. Anselmino, U. D’Alesio, F. Murgia, et al. Yuji Goto (RIKEN/RBRC)

  13. 1 1 10 15 10 15 0.1 0.1 Spin physics with polarized primary beam • D-meson • cross section • PYTHIA (6.228) study with PHENIX tune (<kT> = 1.5 GeV/c, Mc = 1.25 GeV/c2, K-factor = 3.5, Q2 = s) • J-PARC: 3-4 order smaller cross section than that at RHIC • can be compensated by higher intensity/luminosity at J-PARC ? Wohri and Lourenco consistent at fixed-target region, too smaller yield (same result as Laurenco’s study) Yuji Goto (RIKEN/RBRC)

  14. Spin physics with polarized primary beam • D-meson • silicon detectors to identify second decay vertex • yield study • 109 proton/sec beam • 10% target • 2×1033 cm-2sec-1 • × 1 week = 103 pb-1 • acceptance 0.05 – 0.3 to cover forward/mid-rapidity/backward polarized beam 1m silicon pixel detectors with magnetic field pT D0 yield pT > 1.5 GeV/c 5.5×106D0 for 103 pb-1 1.5 GeV/c -1 xF 1 -1 xF 1 Yuji Goto (RIKEN/RBRC)

  15. Spin physics with polarized primary beam • D-meson • efficiency study necessary • decay • DCA cut efficiency • detector study necessary • D-meson identification: E/E in silicon ? • trigger • beam intensity / luminosity as high as possible • depending on radiation hardness of detectors, occupancy/multi-collision capability, etc. Yuji Goto (RIKEN/RBRC)

  16. Spin physics with polarized primary beam • Drell-Yan • +- pair with muon identifier and hadron absorber • forward AN • no final-state effect • small cross section • high intensity / luminosity necessary • 1012 proton/sec 1m X. Ji’s presentation yesterday sensitive to Sivers effect at low qT sensitive to higher-twist effect at high qT hadron absorber muon identifier 1m 5m c.m. 90 degree ~ 0.19 radian Yuji Goto (RIKEN/RBRC)

  17. Spin physics with polarized primary beam • Forward/backward/mid-rapidity 0 • larger EM calorimeter • The most forward neutron • zero-degree calorimeter • large asymmetries in collider energies • AN ~ -12% at xF > 0.2 and pT < 0.3 GeV/c at RHIC • physics implication ? 1m larger EM calorimeter 1m 5m Yuji Goto (RIKEN/RBRC)

  18. Spin physics with polarized beam & target • Drell-Yan ALL • anti-quark polarized distribution • LoI L15 for J-PARC presented by S. Sawada chiral quark soliton model prediction Yuji Goto (RIKEN/RBRC)

  19. Spin physics with polarized beam & target • Gluon polarization at large-x • charmonium ALL • J/, c0, c1, c2 • c2: gluon-fusion dominant • produced mainly from helicity 2 state of the gluon fusion • sensitive to g(x) • identified measurement is possible only in the fixed-target experiments • low photon energy of c   + J/ decay • direct-photon ALL Yuji Goto (RIKEN/RBRC)

  20. Detector • E866 dimuon spectrometer • LoI L15 for J-PARC • closed geometry presented by S. Sawada Fermilab Elab = 800 GeV 2×1012 protons / 20 sec Yuji Goto (RIKEN/RBRC)

  21. Detector • NA60 spectrometer • example of silicon spectrometer + muon detector • charm-identification with muon-coincidence CERN Elab = 158 GeV 2×109 protons / 5 sec Yuji Goto (RIKEN/RBRC)

  22. Detector • PHENIX upgrades • technically important • silicon pixel & strip (stripixel) 2008 installation • RIKEN/RBRC group is leading • Si/W calorimeter • RIKEN/RBRC group is participating and supporting 80cm Yuji Goto (RIKEN/RBRC)

  23. Summary • There are rich spin physics programs with J-PARC primary beam, especially related to the orbital anglular momentum component in the nucleon • AN of pions, D-meson, Drell-Yan, neutron, … • and also g at large-x and anti-quark polarization measurements • charmonium, photon, Drell-Yan, … • Physics and detector studies are ongoing • Collaboration with many groups in the world is very important Yuji Goto (RIKEN/RBRC)

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