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W physics @ PHENIX

W physics @ PHENIX. 2009/06/01 Kyoto Univ. / RIKEN Ken’ichi Karatsu. Contents. Proton Spin Structure Probe Proton Spin with W boson W detection @ PHENIX Summary. 1. Proton Spin Structure. Parton polarization function. Proton Spin : ½ = ½Δ ∑ + ΔG + L

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W physics @ PHENIX

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  1. W physics @ PHENIX 2009/06/01 Kyoto Univ. / RIKEN Ken’ichi Karatsu 2009 RHIC & AGS Annual Users’ Meeting

  2. Contents • Proton SpinStructure • Probe Proton Spin with W boson • W detection @ PHENIX • Summary Contents

  3. 1. Proton Spin Structure 1. Proton Spin Structure

  4. Parton polarization function • Proton Spin : ½ = ½Δ∑ + ΔG+ L < about Δ∑= > • The polarization of valence quark (u, d) are well understood but, that of sea quark (anti-u, anti-d, anti-s) are not well constrained • This talk is about the extraction of sea quark polarization by W-boson production DSSV Global Fit (2008) (DIS+SIDIS+pp) DNS Global Fit (2005) 1. Proton Spin Structure

  5. 2. Probe Proton Spin with W boson 2. Probe Proton Spin with W boson

  6. Probe proton spin with W boson • Extract the sea polarization by measuring the Single Spin Asymmetry of W-boson production • W is produced through pure V-A - Chirality is fixed ideal for spin structure studies • W couples to weak charge ~ flavor - Flavor is (almost) fixed ideal for flavor structure studies • No fragmentation for the final state • Asymmetry of W+ -> Δu, Δd-bar • Asymmetry of W- -> Δd, Δu-bar l+ 2. Probe Proton Spin with W boson

  7. 3. W detection @ PHENIX 3. W detection @ PHENIX

  8. The PHENIX Experiment • Philosophy (initial design): • High rate capability & granularity • Good mass resolution & particle ID • Sacrifice acceptance Central Arm e+/- Muon Arm: Muon Tracking Detector (MuTr), Muon Identifier (MuID) Rapidity: 1.2 < η <2.2 (2.4) Δφ = 2 π Muon Arm Rapidity: |h| < 0.35 Δφ = 2 * (π/2) μ+/- Central Arm: Drift Chamber (DC), Pad Chamber (PC), Ring Imaging Cherenkov Counter (RICH), Electromagnetic Calorimeter (Emc), HBD, TOF, TEC RPCs 3. W detection @ PHENIX

  9. Expected Asymmetry of W production in the PHENIX Acceptance (l- pT>20 GeV) (l+ pT>20 GeV) Muon Arms: trigger upgrade is ongoing  will be ready for next 500 GeV run Central Arms: ready for W measurement 3. W detection @ PHENIX

  10. W in the PHENIX Muon Arms 3. W detection @ PHENIX

  11. μ+/- RPCs W in the PHENIX Muon Arms Muon pT spectra in the Muon Arms (2000 [1/pb], from PYTHIA5.7) recorded luminosity ○ 300[pb-1] Forward AL μ+ Forward AL μ- W is dominant (pT>20 [GeV/c]) W Backward AL μ+ Backward AL μ- Right plot: expected asymmetry of W (assuming 60 % polarization, backgrounds and detector resolution included) from RHICBOS 3. W detection @ PHENIX

  12. W in the PHENIX Muon Arms Design Luminosity √s = 500 GeV σ=60mb L = 2x1032/cm2/s Muon pT spectra in the Muon Arms (2000 [1/pb], from PYTHIA5.7) MuID LL1 pmuon>1.5 [GeV/c] Total interaction rate= 12MHz New Trigger DAQ LIMIT = 2kHz (for Muon Arm) W Required RF ６０００ BUT • Need Momentum Selectivity in the LVL-1 Trigger! MuID LL1 (trigger) RF < 200 3.W detection @ PHENIX

  13. RPC B PHENIX Muon Trigger Upgrade Rapidity: 1.2 < h <2.2 (2.4) New MuTr FEE (MuTRG) Installed & operated at 2009 RHIC Run Prototype RPC Installed & operated at 2009 RHIC Run • New MuTr FEE was installed fully in North Arm and partially in South Arm • Prototype RPC was installed in South Arm • Prototype Pb absorber was installed in South Arm • -> part of South Arm has the full configuration (MuTRG+RPC+Pb) in 2009 RHIC Run! • -> Evaluate the performance with beam of s=500 GeV @ 2009 RHIC Run Prototype Pb absorber Installed at 2009 RHIC Run • MuTRG • use highly segmented • Muon Tracker (good • momentum selectivity) • poor time resolution.. • (> 1 beam crossing) • <Muon Trigger Upgrade> • MuTr FEE Upgrade (MuTRG) • Install RPC (Resistive Plate Chamber) • Install additional Pb absorber • MuID • - only existing trigger • no momentum selectivity.. Basic Idea: Measure Δstrip in online level -> more momentum selective trigger • RPC • add better timing! • less background sensitivity • Pb absorber • reject hadron background 3. W detection @ PHENIX

  14. MuTr St3 MuTr St2 MuTr St1 Current Status - Muon Arms • Performance of New MuTr FEE (MuTRG) • Turn on Point of Efficiency Curve ~ 4 (arb. unit) • Most Probable Value of MIP ~ 20 (arb. unit) • MuTRG and MuTr have matching properly • Efficiency for MIP is 97.5%(Yellow / Blue) • Study of rejection factor is ongoing Trigger Emulation (offline analysis) Blue : MIP dist. Yellow : MIP x Eff. Collision Point Red : MuTRG Hit, Blue : Accepted Track 3. W detection @ PHENIX

  15. RPC3 (Prototype) RPC2 (Prototype) Peak(>0) Peak (<0) Current Status - Muon Arms • Performance of Prototype RPC From collision or out going beam From beam background Peak (<0) : Tracks coming from collision or outgoing beam Peak (>0) : Background by incoming beam Width of each peak : 3 [ns] -> good timing resolution! 3. W detection @ PHENIX

  16. W in the PHENIX Central Arms 3. W detection @ PHENIX

  17. e+/- W in the PHENIX Central Arms pions: NLO pQCD calculation from W. Vogelsang W: RHICBOS (Nadolsky, Yuan) pi+ Upper plot: cross section of e+/- from W & π+/- in the PHENIX acceptance Rapidity: |h| < 0.35 pi+ <Charged hadron rejection> EMCal intrinsic: 50-150 Shower profile: 2-4 Isolation cut: ~10 Total: 1000-6000 e+ e- Lower plot: expected asymmetry of W (assuming 70 % polarization, no background or detector resolution included) recorded luminosity ● 300 [pb-1] ○ 70 [pb-1] 3. W detection @ PHENIX

  18. Current Status - Central Arms pi+ pi+ • Brief summary of 2009 RHIC Run (Run9) • Polarization: ~35[%] (from RHIC pol-group) • recorded luminosity @ PHENIX: ~10 [pb-1] (with vertex cut) • The aim of Run9 analysis -> measure cross section of W boson! (W+e+& W-e-) e+ e- 3. W detection @ PHENIX

  19. e+/- Current Status - Central Arms Energy v.s. Inclination of the track pi+ Emc Energy calibration -> Done Invariant mass v.s. total energy of 2 photons negative charge pi+ • <To do> • estimate detector eff. & acceptance • estimate backgrounds • isolation cut • estimate charge contamination • etc.. • ->lots of things are work in progress now alpha [rad.] ~ 0.1/ mom [GeV/c] “energy / mom < 3” cut applied e+ e- positive charge eta Energy dist. (Black: +, Red: -) Inclination angle (alpha) Only analyzed part of data set pi0 3. W detection @ PHENIX

  20. Event Display of High energy events Energy v.s. Inclination of the track Found W candidates. Analysis is under way! Energy dist. (Black: +, Red: -) 3. W detection @ PHENIX

  21. 4. Summary • W bosons provide possibilities for flavor separated measurements -> sensitive to the polarization of sea quark! • Upgrades are ongoing to measure W boson in the PHENIX Muon Arms. They have been partially installed & tested at 2009 RHIC Run -> Ready for the next 500 GeV run! • W boson measurements in the PHENIX Central Arms is possible and analysis is under way on 2009 RHIC data -> W candidates are seen! 4. Summary

  22. Back up

  23. Pol. Proton proton • Flavor is almost fixed W production • We can extract the sea polarization from Single Spin Asymmetry of W production!! • No fragmentaion for the final state! • W is produced from left-handed q and right-handed q-bar • No W founded to coupled to right-handed current

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