Overview of spin physics results from PHENIX experiment The 4th International Workshop of High Energy Physics in the LHC Era Valparaiso, Chile January 4-10, 2012 Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

Overview of spin physics results from PHENIX experiment The 4th International Workshop of High Energy Physics in the LHC Era Valparaiso, Chile January 4-10, 2012 Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

What are we aiming at? To study protons spin structure The flagship question: Where the proton spin comes from? –Proton spin puzzle –Helicity distribution of partons in longitudinally polarized protons, especially gluons –Flavor-decomposed quark helicity distribution using Ws Whats there in transversely polarized protons? – q q –Very hot recently –Needs more than simple collinear picture to understand 4

The Relativistic Heavy Ion Collider accelerator complex at Brookhaven National Laboratory PHENIX STAR Brahms pp2pp 5

RHIC p+p accelerator complex BRAHMS & PP2PP STAR PHENIX AGS LINAC BOOSTER Pol. Proton Source Spin Rotators 20% Snake Siberian Snakes 200 MeV polarimeter Rf Dipoles RHIC pC CNI polarimeters PHOBOS RHIC absolute pH polarimeter Siberian Snakes AGS pC CNI polarimeter 5% Snake Coulomb-Nuclear Interference 6

PHENIX Experiment Pioneering High Energy Nuclear Interaction EXperiment 7

13 Countries; 70 Institutions Abilene Christian University, Abilene, TX 79699, U.S. Baruch College, CUNY, New York City, NY , U.S. Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY , U.S. Physics Department, Brookhaven National Laboratory, Upton, NY , U.S. University of California - Riverside, Riverside, CA 92521, U.S. University of Colorado, Boulder, CO 80309, U.S. Columbia University, New York, NY 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 , U.S. Morgan State University, Baltimore, MD 21251, U.S. Muhlenberg College, Allentown, PA , 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 , U.S. Chemistry Department, Stony Brook University,SUNY, Stony Brook, NY , 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. Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP , 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, , Prague, Czech Republic Czech Technical University, Zikova 4, Prague 6, Czech Republic Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 8, Czech Republic Helsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI 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, 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 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 , India Bhabha Atomic Research Centre, Bombay , India Weizmann Institute, Rehovot 76100, Israel Center for Nuclear Study, Graduate School of Science, University of Tokyo, Hongo, Bunkyo, Tokyo , Japan Hiroshima University, Kagamiyama, Higashi-Hiroshima , Japan KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki , Japan Kyoto University, Kyoto , Japan Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki , Japan RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama , Japan Physics Department, Rikkyo University, Nishi-Ikebukuro, Toshima, Tokyo , Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo , Japan Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan Chonbuk National University, Jeonju, Korea Ewha Womans University, Seoul , Korea Hanyang University, Seoul , Korea KAERI, Cyclotron Application Laboratory, Seoul, South Korea Korea University, Seoul, , Korea Myongji University, Yongin, Kyonggido , Korea Department of Physocs and Astronomy, Seoul National University, Seoul, South Korea Yonsei University, IPAP, Seoul , Korea IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, , Russia INR_RAS, Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a, Moscow , Russia Joint Institute for Nuclear Research, Dubna, Moscow Region, Russia Russian Research Center "Kurchatov Institute", Moscow, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, , Russia Saint Petersburg State Polytechnic University, St. Petersburg, Russia Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow , Russia Department of Physics, Lund University, Box 118, SE Lund, Sweden Feb 2011

The PHENIX Detector Philosophy –high resolution & high-rate at the cost of acceptance –trigger for rare events Central Arms –| | < 0.35, ~ –Momentum, Energy, PID Muon Arms –1.2 < | | < 2.4 –Momentum (MuTr) Muon piston calorimeter –3.1 < | | < 3.9 9

PART 1: Helicity distribution with longitudinal polarization

Helicity distribution Lepton deep inelastic scattering (DIS) experiments –Quasi-elastic scattering of quark and lepton at high energies where perturbation is applicable –Reaction depends on quark spin spin structure function

Proton spin puzzle Quark spin carries only 20-30% of the nucleon spin spin puzzle (crisis) What carries the rest? –Gluon spin? –Orbital angular momentum? Our Main Goal

What we cant know from DIS Photon mediated sensitive to charge 2 –u : d : s : g = 4 : 1 : 1 : 0 –Gluon is invisible! (c.f., indirect methods: Q 2 evolution, photon-gluon fusion) Can we see gluons directly? Yes, what we need is a Polarized Proton collider 13

What we measure? ~ (parton pol.) 2 × (a LL in parton reaction) 14

How can we access gluons? Typical parton level diagrams LO What we actually measure are not partons, but fragmented hadrons –Come from different mix of partons –Parton information e.g., Bjorken x is obscured 15

Some examples Direct photon: g + q + q –No fragmentation –Small contamination (e.g. qq ) Jet, high-p T hadron production –Mix of all subprocesses –LO highest statistics Good measurement with lower luminosity Heavy quarks (charm, bottom) –gg qq is the main process at RHIC W sensitive to quark flavors –e.g., W + comes from du 16

Accumulated data Year s [GeV] Recorded LPol [%] FOM (P 4 L) 2003 (Run 3) pb nb (Run 4) pb nb (Run 5) pb pb (Run 6) pb pb (Run 6) pb nb (Run 9)20016 pb pb (Run 9)50010 pb pb (Run 11)50017 pb pb -1 with longitudinal polarization 17

Results 18 Run5 Run6 Run9 Precision reaches O(10 -3 ), but still consistent with 0 asymmetry 0 A GeV

How to extract g(x)? (1) 0 s come from quarks and gluons of various x Deconvolution necessary Are we sure that we understand contribution of partons? YES! –NLO-pQCD calculation reproduces GeV, ~0 PRD76:051106,

How to extract g(x)? (2) Practical analysis –Assume functional form: e.g., g(x)=Cg(x)x (1-x) –Search optimum parameters using data, including DIS. Ex GRSV M. Gluck et al., PRD 63 (2001) – Assume G, other parameters are determined from DIS. – Several versions for various G GRSV-std, max, min,... Several other analyses –For the same integral, G, g(x) could be very different –Our measurement mostly constrains G [0.02,0.3] 20

G: Global Fit 21 RHIC data DSSV analysis (Run 9 data not taken into account) Phys. Rev. Lett. 101, (2008) Uncertainty estimation: 2 =1 2 / 2 =2% Node in g(x)?

Global Fit including Run9 0 A LL By S.Taneja et al (DIS2011) ala DSSV with slightly different uncertainty evaluation approach DSSV DSSV + PHENIX Run9 0 A LL No node … Uncertainties decreased A node at x~0.1 ? 22

Extend x-range different s GeV/c 4-5 GeV/c 9-12 GeV/c GeV/c 4-5 GeV/c 9-12 GeV/c 0 at | |<0.35: x g distribution vs p T bin s=500 GeV s=62 GeV s=200 GeV 23

0 at s=62 and 500 GeV: Unpolarized cross section s=500 GeV: PHENIX Preliminary May need inclusion of NLL to NLO s=62 GeV: PHENIX, PRD79, Data below NLO at =p T by (30 15)% 24

at s=62 GeV Charged hadrons Very limited data sample (0.04 pb -1, compared 2.5 pb -1 from Run2005 s=200 GeV) Clear statistical improvement at larger x; extends the range to higher x (0.06<x< 0.4) Overlap with 200 GeV A LL provides measurements at the same x but different scale (p T or Q 2 ) s=500 GeV A LL results will be available soon (from Run2009 with L~10 pb -1 and P~0.4) 0: PHENIX, PRD79,

Forward Calorimetry: MPC Muon Piston Calorimeter (3.1 < |h| < 3.9) : lower x Cluster ( dominant) A LL Decay photon π 0 Direct photon PTPT Fraction of clusters

Parity Violation Asymmetry Clean flavor separation w/o fragmentation uncertainty W measurement

W e in mid-rapidity Phys. Rev. Lett. 106, (2011)

W asymmetry 29 e+e+ e-e- Uncertainty is still large More data in 2011 and from now Run 9 data

30 Forward New Trigger System MuTRG ADTX MuTRG MRG Level 1 Trigger Board MuTr FEE Resistive Plate Counter (RPC) (Φ segmented) B 2 planes 5% 95% Trigger Interaction Region Rack Room Optical 1.2Gbps Amp/Discri. Transmit Data Merge MuTRG RPC FEE Trigger events with straight track (e.g. strip <= 1) RPC / MuTRG data are also recorded on disk. SG1

31 OK: plateau eff. 92% Trigger efficiency Run11 data under analysis results coming soon More results... no time to show them all

Part 2: Transverse spin physics 32

Transverse spin physics Transversity q: Due to Einsteins relativity, not the same as q –Unexplored leading twist PDF A N left-right asymmetry wrt transverse polarization x F <0 x F >0 R L Left Right 33

Requirements for A N Helicity flip amplitude & relative phase In QCD, helicity is conserved if m q =0. A N ~ s m q /p T ~ O(10 -3 ) in naive collinear picture

Reality However, large A N observed in forward pions. WHY?? We need something more hot topic 35

(ii) Collins mechanism: Transversity (quark polarization) × jet fragmentation asymmetry (i) Sivers mechanism: correlation between proton spin & parton k T SPSP p p SqSq k T, π Possible mechanisms (ex.) SPSP k T,q p p SqSq Phys Rev D41 (1990) 83; 43 (1991) 261 Nucl Phys B396 (1993) (iii) Twist 3: quark-gluon/gluon-gluon correlation A source for Sivers function Expectation: at large p T, A N ~ 1/p T – not observed so far

Forward -- MPC 37 A N

200 GeV Same tendency with other energies and experiments 38 Cluster ( dominant) A N

Forward A N 39

Forward A N 40 same tendency with

Comparison with STAR Quite different at high x F Due to slightly different kinematic conditions? Need confirmation/ deconfirmation 41

Midrapidity hadrons A N A N is zero within 0.1% contrast with forward hadrons 42

43 IFF and Collins FF Collins fragmentation function Interference fragmentation function h1h1 h1h1 h2h2 quark h2h2 quark _ Quark spin J. Collins, S.Heppelmann, G. Ladinsky, Nuclear Physics B, 420 (1994) 565 h quark h quark _ (courtesy A. Bacchetta) J. C. Collins, Nucl. Phys. B396, (1993) 161 FF measurements are ongoing at KEK-BELLE

Asymmetry result More results... again, no time to show them all 44 Still need more data...

Part 3: Future measurements 45

More data! Goal: > GeV, > 300 pb 500 GeV 46 mid rapidity 0 MPC GeV 300 pb -1 P=0.55 forward 0

W in forward 47

48 More detectors – (F)VTX VTX barrel | |<1.2 FVTX More will be discussed by J. Seele this afternoon

49 Even further upgrade -- sPHENIX Details will be discussed by J. Seele this afternoon Forward region is important for spin physics -A N in forward regions - g(x) in small x region Compact, hermetic, EM + hadron calorimetry

Summary Gluon polarization –Significant constraints on g(x) for 0.02<x<0.3 –Extension toward lower x is important higher energy, forward region Flavor decomposed quark distribution via W –W e observed in central arm, muon arm follows Transverse spin physics –Trying to find the mechanism to produce large A N in forward region –Access transversity More data are still to come 50