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Spin asymmetry of neutron at zero degree in polarized proton collisions

Spin asymmetry of neutron at zero degree in polarized proton collisions. International workshop on High-energy scattering at zero degree@Nagoya Univ. Mar. 2, 2013 Kiyoshi Tanida (Seoul National University) for PHENIX collaboration.

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Spin asymmetry of neutron at zero degree in polarized proton collisions

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  1. Spin asymmetry of neutron at zero degree in polarized proton collisions International workshop on High-energy scattering at zero degree@Nagoya Univ. Mar. 2, 2013 Kiyoshi Tanida (Seoul National University) for PHENIX collaboration

  2. Spin asymmetry of neutron near zero degree in polarized proton collisions International workshop on High-energy scattering at zero degree@Nagoya Univ. Mar. 2, 2013 Kiyoshi Tanida (Seoul National University) for PHENIX collaboration

  3. Introduction • How most forward particles are produced in pp collisions? • High energy, yet non-perturbative (pT < 1 GeV/c) • Regge theory? • Explains total cross sectionin high-energypp collisionwith Pomeron • How about observablesother than totalcross section?

  4. xF Nucl. Phys. B109 (1976) 347-356 Forward n production • Cross section: peak around xF ~ 0.8 • Only at pT~0, almost independent of √s

  5. One-pion exchange model E.g.: N. N. Nikolaev et al., PRD 60, 014004 (1999) p r, a2 pDn BG (xF) OPE modelsseem OK

  6. Single spin asymmetry AN Left xF<0 xF>0 L R Right • Left-right asymmetry (forward = beam direction,up = spin direction) Interaction LR definition

  7. How An is produced? • Need both helicity flip & non-flip amplitudes • In Regge theory • Pionexchange givesspin flip • Non flip? Other reggeons? • Sensitive to mechanism

  8. Brhams pp2pp PHENIX STAR The Relativistic Heavy Ion Collider accelerator complex at Brookhaven National Laboratory

  9. RHIC p+p accelerator complex RHIC pC “CNI” polarimeters absolute pH polarimeter BRAHMS & PP2PP PHOBOS RHIC Siberian Snakes PHENIX STAR Siberian Snakes Spin Rotators 5% Snake LINAC BOOSTER AGS pC “CNI” polarimeter Pol. Proton Source AGS Coulomb-Nuclear Interference 200 MeV polarimeter Rf Dipoles 20% Snake

  10. Hadron Cal Post shower counter Gamma veto (plastic scinti.) Lead block First measurement＠IP12 2001～2002＠√s=200 GeV ～1800cm ±2.8mrad Dx magnet 10cm Blue beam yellow beam EM Cal hodoscope Steel Charged veto (plastic scinti.) To measure Collision point Neutron veto (plastic scinti.)

  11. EM calorimeter • Performance • E/E ~ 10%/E(GeV) for  • x ~ y ~ 0.1 cm for  • x ~ y ~ 0.5 cm for neutron

  12. invariant mass of pairs of energy clusters Result • Phys. Lett. B 650 (2007) 325.

  13. Hadron calorimeter • One ZDC prototype module (1/3 length) • Performance • Energy is calibrated by using cosmic-ray data and simulation. • E/E ~ 40-50% at E > 20 GeV • x ~ 3 to 4 cm by the post shower counter

  14. IP12 experimentsummary • Forward neutron – Large asymmetry discovered • EMCal result AN = 0.0900.0060.009 • HCal result AN = 0.1350.018 • consistent at the 2-level • 0 and photon • AN consistent with zero • backward asymmetries • AN consistent with zero

  15. PHENIXExperiment Pioneering High Energy Nuclear Interaction EXperiment

  16. Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, Brazil Institute of Physics, Academia Sinica, Taipei 11529, Taiwan China Institute of Atomic Energy (CIAE), Beijing, People's Republic of China Peking University, Beijing, People's Republic of China Charles University, Ovocnytrh 5, Praha 1, 116 36, Prague, Czech Republic Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic Helsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, Finland Dapnia, CEA Saclay, F-91191, Gif-sur-Yvette, France Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, France Laboratoire de Physique Corpusculaire (LPC), Université Blaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 Aubiere Cedex, France IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary ELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, Hungary KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, Hungary Department of Physics, Banaras Hindu University, Varanasi 221005, India Bhabha Atomic Research Centre, Bombay 400 085, India Weizmann Institute, Rehovot 76100, Israel Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Kyoto University, Kyoto 606-8502, Japan Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan Chonbuk National University, Jeonju, Korea Ewha Womans University, Seoul 120-750, Korea Hanyang University, Seoul 133-792, Korea KAERI, Cyclotron Application Laboratory, Seoul, South Korea Korea University, Seoul, 136-701, Korea Myongji University, Yongin, Kyonggido 449-728, Korea Department of Physocs and Astronomy, Seoul National University, Seoul, South Korea Yonsei University, IPAP, Seoul 120-749, Korea IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia INR_RAS, Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia Russian Research Center "Kurchatov Institute", Moscow, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia Saint Petersburg State Polytechnic University, St. Petersburg, Russia Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119992, Russia Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden 13 Countries; 70 Institutions Feb 2011 Abilene Christian University, Abilene, TX 79699, U.S. Baruch College, CUNY, New York City, NY 10010-5518, U.S. Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. University of California - Riverside, Riverside, CA 92521, U.S. University of Colorado, Boulder, CO 80309, U.S. Columbia University, New York, NY 10027 and Nevis Laboratories, Irvington, NY 10533, U.S. Florida Institute of Technology, Melbourne, FL 32901, U.S. Florida State University, Tallahassee, FL 32306, U.S. Georgia State University, Atlanta, GA 30303, U.S. University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S. Iowa State University, Ames, IA 50011, U.S. Lawrence Livermore National Laboratory, Livermore, CA 94550, U.S. Los Alamos National Laboratory, Los Alamos, NM 87545, U.S. University of Maryland, College Park, MD 20742, U.S. Department of Physics, University of Massachusetts, Amherst, MA 01003-9337, U.S. Morgan State University, Baltimore, MD 21251, U.S. Muhlenberg College, Allentown, PA 18104-5586, U.S. University of New Mexico, Albuquerque, NM 87131, U.S. New Mexico State University, Las Cruces, NM 88003, U.S. Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S. Department of Physics and Astronomy, Ohio University, Athens, OH 45701, U.S. RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. Chemistry Department, Stony Brook University,SUNY, Stony Brook, NY 11794-3400, U.S. Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, NY 11794, U.S. University of Tennessee, Knoxville, TN 37996, U.S. Vanderbilt University, Nashville, TN 37235, U.S.

  17. PHENIX Detector • Philosophy • high resolution & high-rate at the cost of acceptance • trigger for rare events • Central Arms • |h| < 0.35, Df ~ p • Momentum, Energy, PID • Muon Arms • 1.2 < |h| < 2.4 • Momentum (MuTr) • Muon piston calorimeter • 3.1 < |h| < 3.9

  18. ZDC Forward counter SMD 1 ZDC 3 modules: 150X0 5.1λI ZDC ～1800cm 10cm blue beam yellow beam ±3 mrad Dx magnet SMD BBC position measurement with scintillators 5.1λT 149X0 (3 ZDCs), dE/E~ 20% @ 100GeV

  19. SMD 2nd ZDC module Shower Maximum Detector • Arrays of plastic scintillators • Position given as shower center • position resolution ~1cm @ 50GeV neutron (mm) 100 5 150 Hadron shower x: segmented by 7 y: segmented by 8

  20. South North ⊿φ = 2π 144.35 cm BBC • Quartz Cherenkov counter • 2 identical parts (BBC-north and -south) • 64 segments each. • Trigger on associated particles

  21. Cross section@s = 200 GeV • Consistent withresults at lowerenergy xF scaling works well • OPE model stillvalid arXiv:1209.3283

  22. charged particles neutron neutron AN at s = 200 GeV ZDC trigger Forward asymmetry AN = 0.0610.010(stat)0.004(syst) ZDC trigger Backward asymmetry AN = 0.0060.011(stat)0.004(syst) ZDCBBC trigger Forward asymmetry AN = 0.0080.005(stat)0.004(syst) ZDCBBC trigger Forward asymmetry AN = 0.0750.004(stat)0.004(syst)

  23. Local Polarimeter Forward neutron AN is used to know the spin direction at the PHENIX collision point PHENIX Spin Rotators change the direction of spin from up/downto forward/backward

  24. Vertical polarization at PHENIX (Raw Asymmetry) / (beam pol.) ø ø BLUE YELLOW

  25. Radial polarization at PHENIX (Raw Asymmetry) / (beam pol.) ø ø BLUE YELLOW

  26. Longitudinal polarization at PHENIX (Raw Asymmetry) / (beam pol.) ø ø BLUE YELLOW

  27. How about associated particles? • Asymmetry is 0 when data is selected by BBC only. • Tag on forward n → finite AN observed • Backward particles： (2.28±0.55±0.10)×10-2（4s） • Forward particles： (-4.50±0.50±0.22)×10-2（9s）(preliminary) Top view pion exchange model Y : charged particles Y’ polarized proton proton Y n (neutron) Y pol direction N*(D*)  n+Y ?? AN(Y) < 0, AN(Y’) > 0 N* ???

  28. xF Dependence ZDC trigger arXiv:1209.3283 • No xF dependence observed ZDCBBC trigger

  29. s Dependence (1) Inclusive neutron

  30. sDependence (2) Neutron with charged particles

  31. pT Dependence (1) Inclusive neutron

  32. pT Dependence (2) Neutron with charged particles

  33. Discussion • Observed AN is larger for largers • Can be interpreted as pT dependence pT ~ (s/2)・xF・q (Note: AN = 0 at pT = 0) • On the other hand, xF dependence was not seen. • Same tendency was observed with and without coincident particles in BBC (3.0 < |h| < 3.9), though the amplitude is slightly different

  34. Comparison with model (1) • OPE model calculationfailed to reproduce • No sign change • There must be somethingbeyond simple OPE • Other reggeons? xF = 0.6~0.9 pT (GeV/c) B.Z. Kopeliovich et al.arXiv:0807.1449

  35. Comparison with model (2) • Pion-a1 interference • Good agreement withdata • Interference btwspin flip/non-flip small amplitude can make big difference • Kopeliovich et al., PRD 84 (2011) 114012. • Also in Soffer’s talk in this workshop

  36. Summary & Perspective • Neutron AN near 0 degree • s and pT dependence were measured • Significant s and pT dependence was observed, while no xF dependence was seen • s dependence can be understood as pT dependence • One pion exchange model expects AN~0 around the pT region • Can be explained by other reggeons, such as a1 • Interference  sensitive to small amplitudes • Need data for higher pT • AN∝ pT is inevitable in low pT • At which pT is AN maximum?

  37. Backup slides

  38. Cross section

  39. Cross section calculation

  40. s dependence backward forward • Neutron with charged particles

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