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Enhancing the W Physics Program at PHENIX: Techniques and Studies on Parity Violating Spin Asymmetries

The PHENIX workshop emphasizes the motivation and advancements in the W physics program, focusing on sea polarization and quark flavor in parity-violating decays. Critical developments include high-luminosity operations at √s=500 GeV, necessary muon trigger upgrades, and strategies to mitigate background noise. Innovative detector upgrades, including Resistive Plate Counters (RPCs), enhance muon detection capabilities, while addressing challenges like space limitations and high rate handling. This collaborative effort involves contributions from global institutions, aiming to improve measurements and theoretical understanding of spin asymmetries.

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Enhancing the W Physics Program at PHENIX: Techniques and Studies on Parity Violating Spin Asymmetries

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  1. The W program at PHENIX Workshop on Parity Violating Spin Asymmetries BNL, April 26-27th R. Seidl (University of Illinois and RBRC) for the PHENIX Collaboration

  2. Motivation for W physics I: sea polarization • Parity violating decay selects quark flavor: • Forward/backward region selects valence/sea quark helicity contribution • High luminosity and high √s=500 GeV needed • Only m± detected  control of backgrounds important • High energy muon trigger necessary • Advantages of W as probe: • Large Scale ( ~mW) • no Fragmentation functions required R.Seidl:The W physics program at PHENIX

  3. Motivation for W physics II: asymmetric (unpolarized) sea? • Asymmetry between d(x) and u(x) seen at E866, HERMES and NA51 • Test asymmetry in W production w/o possible nuclear effects • Also high-x behavior of u(x)/d(x) can be tested R.Seidl:The W physics program at PHENIX

  4. The PHENIX Detector • Philosophy (initial design): • High rate capability & granularity • Good mass resolution & particle ID • Sacrifice acceptance • p0/g/h detection • Electromagnetic Calorimeter • p+/p- • Drift Chamber • Ring Imaging Čerenkov Counter • Heavy quarks • Muon Id/Muon Tracker • Relative Luminosity • Beam Beam Counter (BBC) • Zero Degree Calorimeter(ZDC) • Local Polarimetry - ZDC R.Seidl:The W physics program at PHENIX

  5. Necessity of muon trigger upgrade • Hadronic decays dominate muon rates • W dominate only above 20-25 GeV • DAQ cannot take full rate @500GeV • Current muon trigger momentum “blind” • Need for a momentum sensitive muon trigger • Add Resistive Plate Counters(RPCs) • Add fast readout electronics for Muon tracker R.Seidl:The W physics program at PHENIX

  6. RPC2 RPC3 • Three dedicated trigger RPC stations (CMS design): • RPC1(a,b): ~180 segments inj, 2 in θ • RPC2: ~360 segments in j, 2 in θ • RPC3: ~360 segments in j, 2 inθ • (Trigger only – offline segmentation higher) RPC1(a+b) NSF (Funded) r=3.40m MuTr • MuTr front end electronics • Upgrade to allow LL1 information JSPS (Funded) PHENIX muon trigger upgrade R.Seidl:The W physics program at PHENIX

  7. Resistive Plate Counters -HV GND GND -HV Challenges: • Equip large areas (RPC2 ~22 m2) • Limited space (smallest ~30cm) • Varying rates from pp to Heavy Ion  Bakkelite RPCs: • Modules can cover larger area • Lower resistivity than glass  higher rate capability • Thickness of a module only ~3cm Readout Collaborative effort between groups in Korea, China, several American universities and BNL R.Seidl:The W physics program at PHENIX

  8. Limited space for installation • RPC2 R.Seidl:The W physics program at PHENIX

  9. Sideview of PHENIX with RPCs RPC3 South RPC2 South RPC2 North RPC3 North R.Seidl:The W physics program at PHENIX

  10. New MuTRG Front End Electronics(FEE) MuTRG-TX MuTRG-AD MuTr Chamber Current FEE R.Seidl:The W physics program at PHENIX

  11. Offline backgrounds in W analysis • Cosmic muons • Reliable rates not available • First tests suggest a small rate • Muons from Z/g decays • Z have small x-section • Z sensitive to quark helicities • Fake high PT muons from low PT hadron decays R.Seidl:The W physics program at PHENIX

  12. How to address fake high PT hadrons I: Absorber • At early stage (2009-2010) additional absorber instead of RPC1 to reduce rate • Maybe already install Tungsten instead of Cu in the nosecone ( needed for Nose Cone Calorimeter ) R.Seidl:The W physics program at PHENIX

  13. How to address fake high PT hadronsII:The PHENIX NoseCone Calorimeter (NCC) Electromagnetic Preshower and Shower-Max Hadronic • g+e identification • g – p0 separation • e/m isolation • jet identification • dE/dx • e/g/jet triggers Fake hadron reduction NCC R.Seidl:The W physics program at PHENIX

  14. How to address fake high PT hadrons III:The forward Vertex detector • Baseline: • 4 layers • Vertical planes • 75 m radial pitch, 7.5° phi segmentation (2 – 13 mm) • Maximize z and r extent to give good resolution and ≥3 hits/track as much as possible • 2*600K channels • Scope • Recently favorably reviewed for FY08 start • Bootstrapped by LANL LDRD funds to construct one octant prototype • Submitted proposal to DOE for FY08 funding start • New Idea on hadron suppression for W physics: • Average dE/dx in 3 planes can distinguish low energetic hadrons and high energetic muons R.Seidl:The W physics program at PHENIX

  15. PHENIX ALW+/-Sensitivity Expected Sensitivity with W measurement • Machine and detector requirements: • ∫Ldt=800pb-1, P=0.7 at √s=500 GeV • Muon trigger upgrade! 2009 to 2012 running at √s=500 GeV is projected to deliver ∫Ldt ~980pb-1 R.Seidl:The W physics program at PHENIX

  16. vs HERMES • SIDIS: • large x-coverage • uncertainties from • Fragmentation functions • W-physics: • limited x-coverage • High Q2 theoretically • clean • No FF-info needed R.Seidl:The W physics program at PHENIX

  17. Upgrade Schedule R&D Phase Construction Phase Ready for Data R.Seidl:The W physics program at PHENIX

  18. Physics Timeline see Spin report to DOE http://spin.riken.bnl.gov/rsc/ L= 1x1031cm-2s-1 6x1031cm-2s-1 1.6x1032cm-2s-1 P= 0.5 0.6 0.7 …………………………………… √s= ……………………….. 200 GeV …………………......... 500 GeV| 2005 2006 2007 2008 2009 …. 2012 (RHIC II) 10 pb-1 …………………………………… 275pb-1 …….. 980pb-1 @ 200GeV @ 500GeV Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics direct photons bottom physics W-physics ALL(hadrons, Jets) ALL(charm) ALL(γ) AL(W) R.Seidl:The W physics program at PHENIX

  19. Outlook: strange polarization with RHICII luminosities P1 • At high luminosities possibility to tag strangeness: • Detect muon from W decay (Muon Trigger) • Detect displaced vertex of D meson decay (VTX and FVTX detectors) • Charge of m selects strange/antistrange • More in Yokoya-san’s talk P2 R.Seidl:The W physics program at PHENIX

  20. Summary • Muon Trigger upgrade funded and progressing well • First Test Octant of FEE upgrade will be ready for RUN8 • First new muon Trigger available for run 10 • Additional upgrades will improve offline W analysis R.Seidl:The W physics program at PHENIX

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