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Young Jin Kim f or the PHENIX Collaboration

First measurement and future prospects for measurements of single spin asymmetries in W production with the PHENIX experiment at RHIC. Young Jin Kim f or the PHENIX Collaboration. Outline. Physics motivation Proton spin Single spin asymmetry of W bosons RHIC Accelerator

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Young Jin Kim f or the PHENIX Collaboration

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  1. First measurement and future prospects for measurements of single spin asymmetries in W production with the PHENIX experiment at RHIC Young Jin Kim for the PHENIX Collaboration SPIN-Praha-2010

  2. Outline • Physics motivation • Proton spin • Single spin asymmetry of W bosons • RHIC • Accelerator • PHENIX experiment • Single spin asymmetry of W bosons from RHIC Run-9 • PHENIX forward moun trigger upgrade • MuTRG • RPC • Projection • Summary SPIN-Praha-2010

  3. Physics Motivation SPIN-Praha-2010

  4. Proton Structure u u d • With three valance quarks: • We understand • Charge • Proton = 3 valance quarks + sea quarks + gluons • Momentum: carried by both quarks and gluons • What about proton spin? • Quark spin = ½ • Spin Crisis: • Quark Spin  = 0.24  0.12  0.01 • EMC: Phys. Lett. B 206, 364 (1988); Nucl. Phys. B 328, 1 (1989) quark spin gluon spin orbital angular momentum Spin ½ quarks Spin ½ anti-quarks Spin 1 gluons SPIN-Praha-2010

  5. Quark and Gluon Distribution Functions • Spin dependent quark distribution functions by the QCD analysis of DIS data • : well known • : only known with large uncertainties • Spin dependent gluon distribution function by the QCD analysis of DIS data • G=0.471.08 (largely unknown) • The latest extraction of polarized partondistributions (DSSV): • D. de Florian, R. Sassot, M. Stratmann, W. Vogelsang, Phys. Rev. D 80, 034030 (2009) M. Hirai, S. Kumano, N. Saito, Phys. Rev. D 74, 014015 (2006) SPIN-Praha-2010

  6. Semi-Inclusive DIS: e+p e+ h +X Quark & Anti-Quark Helicity Distributions • How well do we know hadron • fragmentation functions ? • new analysis of e+e- data, • Hirai, Kumano, Nagai, Sudo • hep-ph/0612009, INPC 2007 • Extraction based on LO-QCD inspired QPM at low Q2 • Unspecified uncertainties from possible QCD NLO contributions and/or sub-leading twist • Large uncertainties from fragmentation functions SPIN-Praha-2010

  7. Semi-Inclusive DIS: e+p e+ h +X Quark & Anti-Quark Helicity Distributions • How well do we know hadron • fragmentation functions ? • new analysis of e+e- data, • Hirai, Kumano, Nagai, Sudo • hep-ph/0612009, INPC 2007 • Recent progress on fragmentation functions (DSS): • D. de Florian, M. Stratmann, R. Sassot, Phys. Rev. D76, 074033 (2007) • For the first time: Inclusion of e+e-, SIDIS and pp data in global analysis • Still significant uncertainties in s, heavy flavor and gluon fragmentation function • Several data sets at low Q2: validity of analysis at leading twist OPE and NLO QCD • Extraction based on LO-QCD inspired QPM at low Q2 • Unspecified uncertainties from possible QCD NLO contributions and/or sub-leading twist • Large uncertainties from fragmentation functions SPIN-Praha-2010

  8. Parity Violating W Production • W boson production in p-p collision • Large scale (~mW) • flavor combination is almost fixed • flavor separated measurement • helicities of interacting partons are fixed • spin measurement • W→ lepton decay includes no fragmentation process • direct and cleanmeasurement • Important to control hadron decays and beam backgrounds • Asymmetry measurement of W boson production is ideal method • High luminosity and longitudinally polarized p+p collisions at 500 GeV (integrated L = 300 pb-1, polarity = 70%) SPIN-Praha-2010

  9. Single Spin Asymmetry of W • Forward/backward region selects valance/sea quark helicitycontribution • Flavor decomposed proton quark polarization can be probed using the single spin asymmetry of W+ and W- in longitudinally polarized p+pcollisions SPIN-Praha-2010

  10. Relativistic Heavy Ion Collider (RHIC) and PHENIX SPIN-Praha-2010

  11. Relativistic Heavy Ion Collider (RHIC) BRAHMS PHOBOS PHENIX RHIC, lenght: 3.83 km STAR SPIN-Praha-2010

  12. Relativistic Heavy Ion Collider (RHIC) RHIC is world’s unique polarized proton collider SPIN-Praha-2010

  13. PHENIX Detector e+/- • Philosophy (initial design): • High rate capability & granularity • Good mass resolution & particle ID • Sacrifice acceptance • Central Arms: • hadrons, photons, electrons • |η|<0.35 • Δφ=π(2 arms x π/2) • Global Detectors: • Beam-Beam Counter (BBC) • Zero Degree Calorimeter (ZDC) μ+/- • Muon Arms: • muons • 1.2<|η|<2.2 • Δφ = 2π SPIN-Praha-2010

  14. Expected Single Spin Asymmetry of W in the PHENIX Acceptance m- m+ m+ m- e- e+ Central Arms: W measurement at RHIC Run-9 Muon Arms: Forward muon trigger upgrade is ongoing and ready for RHIC Run-11 SPIN-Praha-2010

  15. W measurement at PHENIX Central Arms SPIN-Praha-2010

  16. W e • EMCal (x~0.01x0.01) 4x4 tower sum trigger • ±30 cm vertex cut • High energy EMCal clusters matched to charged track • Loose timing cut to reduce cosmic ray background • Loose E/p cut e Fully efficient at 12 GeV/c  • RHIC Run-9: First 500 GeV Run, March 17 - April 13, 2009 • Machine development in parallel with physics running to increase luminosity, polarization , reduce backgrounds • Integrated luminosity (with vertex cut) = 8.57 pb-1 • Polarization is <P> = 0.39±0.04 (scale uncertainty) SPIN-Praha-2010

  17. Effect of Cuts Clusters Good track match TOF cut E/p • Smooth spectrum of EMCalclusters after removing bad towers • Have a good track pointing to an EMCalcluster • Timing within start time of collision • Reduces out of time backgrounds (cosmics) by ~80% • E/pcut SPIN-Praha-2010

  18. Expected W  e Decay Signal positive negative RHICBOS: Nadolsky and Yuan, Nucl. Phys. B 666:31-55,2003 • QCD provides the most obvious background (W. Vogelsang) • Not shown here but very important • Cosmics and photons (from meson decays and direct), which can have accidental matches to tracks or conversions • c/b relatively small above 30 GeV, calculated at FONLL (MatteoCarciari) • Z/* background is estimated from PYTHIA (~1 count is expected in Run09). • We is also small SPIN-Praha-2010

  19. Comparison To Measured Spectra + - Data and MC driven BG estimation: EMCal cluster distribution after subtracting cosmic background  (Conversion + Accidental)  Tracking Acceptance • (NLO Hadrons thru Geant + FONLL c/b) • Normalization from fit to 10-20 GeV + • The same scale factor for PYTHIA was used for W/Zshape • W-  e- signal has fewer counts than W+ e+ signal as expected SPIN-Praha-2010

  20. Isolation Cut • Signature of a W event is that it is isolated • Sum up energy in a cone around electron and in cone on opposite hemisphere E < 2GeV + - • 90+% of signal is kept (red histograms) • Factor ~5 reduction in jet dominated region SPIN-Praha-2010

  21. Raw Asymmetries (e+) SPIN-Praha-2010

  22. PHENIX AL(W+ e+) • Using average polarization 0.39±0.04, we get • Asymmetry is corrected for dilution by Z and QCD backgrounds ALW+= -0.83 ± 0.31 SPIN-Praha-2010

  23. PHENIX Forward Muon Trigger Upgrade SPIN-Praha-2010

  24. Current PHENIX Muon Arms MuonID (MuID) • Acceptance • 1.2<|η|<2.2 • Δφ = 2π • MuTr • 80 cm of steel & Copper absorber • 3 stations of cathode strip chamber • 3gap + 3 gap + 2 gap • Each gap has non-stereo and stereo strip plane • Total 16 cathode strip planes • MuID • 5 gaps of larocci tube in x and y directions • Total 80 cm of steel plates • Muon Tracking and triggering • Tracking uses hit positions from each station • Most hadrons are absorbed before reaching MuID last gap • Rejection power of the current MuID based first level trigger ~ 100 Absorber Muon Muon Magnet Hadron MuonTracker (MuTr) SPIN-Praha-2010

  25. PHENIX Muon Arms simulated muons into Muon Arms (2000 pb-1, with PYTHIA 5.7) Design Luminosity √s = 500 GeV σ=60mb L = 1.5x1032cm-2s-1 (L = 3.0x1032cm-2s-1, after luminosity upgrade) Total interaction rate= 9MHz (18 MHz) DAQ LIMIT = 2kHz(for Muon Arm) Required RF = 4500 (9000) MuID LL1 (trigger) = RF < 100 W Current Muon Trigger at PHENIX SPIN-Praha-2010

  26. PHENIX Muon Arms • In order to measure W at 500 GeV, we need a first level rejection factor 9000 • The current muon trigger accepts muons above 2 GeV/c and current DAQ cannot take full rate at 500 GeV • We need a momentum sensitive muon trigger and fast readout electronics for muontracker • NSF funded trigger RPC stations • JSPS funded MuTr front end electronics • Additional RPC and MuTr information in the trigger makes it possible to measure the sagitta of charged particles online • The upgraded first level trigger will select events with muons of high transverse momentum pt 20 GeV/c from W boson decay simulated muons into Muon Arms (2000 pb-1, with PYTHIA 5.7) W Current Muon Trigger at PHENIX SPIN-Praha-2010

  27. PHENIX Muon Trigger Upgrade MuTRG MuTRG RPC 1 RPC 3 RPC 3 • Adding 35 cm Fe absorber: • reduce the lower momentum hadron punch through • (S/B=3:1 instead of 1:3 without absorber) MuTRG (fully installed): Fast selection of high momentum tracks RPC (being installed): Provide timing information and rough position information MuID Trigger (existing): Selecting momentum above 2 Gev/c SPIN-Praha-2010

  28. PHENIX Muon Trigger Upgrade RPC1 RPC3 • Momentum selectivity through online sagitta measurement • Uses MuTr station 1, 2, 3 and RPC station 1, 3 • Implement trigger using fast, parallel logic on FPGA’s • Beam related background rejected by RPC timing information SPIN-Praha-2010

  29. PHENIX Muon Trigger Board Upgrade (MuTRG) Resistive Plate Counter (RPC) (Φ segmented) B Trigger events with straight track (e.g. Dstrip <= 1) Level 1 Trigger Board Trigger RPC FEE MuTRG Data Merge Amp/Discri. Transmit Trigger 5% Optical MuTRG MRG MuTRG ADTX 1.2Gbps Trigger 2 planes RPC / MuTRG data are also recorded on disk MuTr FEE 95% Interaction Region Rack Room SPIN-Praha-2010

  30. PHENIX MuTRG Installation MuTRGRack MuTRGADTX • Completed MuTRG installationand commissioned MuTRG • Evaluation of commissioning data is in progress SPIN-Praha-2010

  31. MuTRG Efficiency for Track 0.939 0.874 = (# of MuTRG)/(# of MuTr hits) Red : Δs=1 Black : Δs=0 8.5 GeV/c 12.2 GeV/c • Sufficient efficiency can be achieved in MuTRG • Turn on point is enough low with Δs=0 • (12.2 GeV/c in p, ~6 GeV/c in pT) SPIN-Praha-2010

  32. PHENIX Muon Trigger RPC • Characteristics of double gap RPC in avalanche mode • Fast response: Suitable for the trigger device • Good time resolution: 1 - 2 ns for M.I.P • Good spatial resolution: typically ~ cm • →Determined by the read-out strip width and cluster size • Efficiency: > 95 % for M.I.P • Rate capability: 1 - 2 kHz/cm2 • Low cost: bakelite (resistivity 1010 - 1011cm) • Noise rate: 0.5 - 5 Hz/cm2 for 1010cm • Typical strip multiplicity: 1.5 - 3 • Typical gas mixture • 95% C2H2F4(Tetrafluoroethane, R134A, base gas for avalanche mode RPC) + 4.5% i-C4H10(isobutane, photon quencher) + 0.5% SF6 (electron quencher) • 20 – 40% relative humidity PHENIX RPC Detector Requirement SPIN-Praha-2010

  33. PHENIX Muon Trigger RPC RPC3 station RPC3 station RPC1(a,b) station RPC3 Use already established CMS Bakelite RPC technology and expertise half octant RPC 3A RPC 1A SPIN-Praha-2010

  34. PHENIX RPC Module QA RPC test stand event display RPC readout strip planes cosmic ray trigger scintillators Raw TDC : 1 unit = 100 ns/44 = 2.41 ns cosmic ray trajectory SPIN-Praha-2010

  35. PHENIX RPC Module Noise Rate • # of strips vs. noise rate • all 48 modules • H.V = 9.5 kV • FEE Threshold = 160 mV • <noise rate> = 0.52 Hz/cm2 • 7 strips are over 10 Hz/cm2 • # of strips vs. noise rate • Individual module • H.V = 9.5 kV • FEE Threshold = 160 mV • Black = module A • Blue = module B • Red = module C All results are compliant with PHENIX RPC requirements SPIN-Praha-2010

  36. PHENIX RPC Half Octant Assembly • RPC half octant placed on half octant assembly table at the RPC factory in BNL • All half octant parts are made of aluminum • Half octant contains three RPC modules • Final cable routing during half octant QA SPIN-Praha-2010

  37. PHENIX RPC Half Octant Noise Rate • <noise rate> = 0.37 Hz/cm2 • Modules are in Faraday cage SPIN-Praha-2010

  38. PHENIX RPC-3 North Installation SPIN-Praha-2010

  39. PHENIX RPC-3 North Installation Completed SPIN-Praha-2010

  40. PHENIX RPC-3 North Integration Completed RPC Integration completed RPC TDC Rack • RPC-3 north was commissioned in Run-10 • Evaluation is in progress SPIN-Praha-2010

  41. PHENIX RPC Prototypes during RHIC Run-9 Prototype RPCs MuTRG MuTRG Absorber Prototype RPC Prototypes Partially installed MuTRG SPIN-Praha-2010

  42. Timing Information from PHENIX RPC Prototype No correction for collision vertex 30 cm ~ 2nsec. Muon cuts: tracks close to RPCs, at least 3 GeV momentum  ~ 4.1ns  ~ 5.3ns • The peak below zero: tracks coming from the collision or the outgoing beam • The other peak above zero: background generated by incoming beam • Separation of the peaks: ~ 12 ns • Width for each peak: 3 ns • Individual RPC timing results required a timing correction from reference detector SPIN-Praha-2010

  43. PHENIX Muon Trigger Upgrade Schedule RPC Installation for Station 3 South by October +Absorber Installation RPC Production for Station 1 North by December RPC Installation for Station 3 North by October RPC Installation for Station 1 during shutdown • PHENIX RPC-3 south production completed • PHENIX RPC-3 south half octant QA is underway • PHENIX will be ready for W measurement for RHIC Run-11 • Completion of RPC Project expected in 2011 SPIN-Praha-2010

  44. RHIC Run-11 AL of W Projection Exceptive Conservative • For RHIC Run-11, asking 10 weeks 500 GeVp+p collisions with 50% of polarization • Expecting integrated luminosity L = 50 pb-1 SPIN-Praha-2010

  45. RHIC Run-11+12 AL of W Projection Exceptive Conservative • For RHIC Run-12, asking 8 weeks 500 GeVp+p collisions with 50% of polarization • Expecting integrated luminosity L = 150 pb-1 (together RHIC-11 and 12) SPIN-Praha-2010

  46. Summary • PHENIX observed W e decay in the mid-rapidity region • First attempt to measure single spin asymmetry has detected a parity violating asymmetry leading to a preliminary value of AL • AL(W+  e+) at |ye| < 0.35 has been measured to be Within errors, it is consistent with the predictions. • While the data sample is small, we got a first significant result • Gained experience on the backgrounds to the W in the PHENIX central arm • Learned how to handle multiple collisions from high luminosity • Learned how to handle very high momentum particles • Working on finalizing cross-sections, AL(W+), and AL(W-) • Goal of the RHIC W program is 300 pb-1 and 70% polarization • Order of magnitude improvement in the error bars • Forward muon measurements in PHENIX will contribute significantly starting next year with MuTRG, RPC, and absorber ALW+= -0.83 ± 0.31 SPIN-Praha-2010

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