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First High p T Physics Prospects with the Photon Spectrometer at ALICE

First High p T Physics Prospects with the Photon Spectrometer at ALICE. Kenta Shigaki (Hiroshima University ) for the ALICE Collaboration 3 rd Joint Meeting of DNP’s of APS and JPS October 14, 2009 Waikoloa, Big Island, Hawaii. Most Relevant Members.

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First High p T Physics Prospects with the Photon Spectrometer at ALICE

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  1. First High pT Physics Prospectswith thePhoton Spectrometer at ALICE Kenta Shigaki (Hiroshima University ) for the ALICE Collaboration 3rd Joint Meeting of DNP’s of APS and JPS October 14, 2009 Waikoloa, Big Island, Hawaii

  2. Most Relevant Members • + all PHOS and PWG4 (jet/photon) collaborators Kenta Shigaki Aya Hiei Hisa Torii Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  3. Presentation Outline • LHC/ALICE/PHOS status and schedule • high pT neutral mesons in first year of ALICE • statistics and pT reach • technical challenges and resolutions • first high pT physics prospects • p0 in Pb+Pb run in 2010 • more work in progress • summary and concluding remarks Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  4. LHC/ALICE/PHOS Status & Schedule • collisions in 2009/12; physics awaited in 2010 • ALICE under commissioning • cosmic data taking ongoing • LHC beam (p and Pb) also seen • 3(/5) PHOS modules installed; being cooled down September, 2009 Pb beam injection oriented Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  5. Jet Quenching at LHC • higher pT reach + stronger suppression than RHIC • clearer measurement of quark energy loss • e.g. quark flavor/spin dependent suppression? • “day-1” ALICE physics program • enough acceptance with initial 3 PHOS modules Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  6. Statistics + pT Reach in 1st p+p Run • assumptions: • 10 TeV p+p; 5×1028 cm-2s-1; 180 days×10% • p0 in NLO/CTEQ6M/KKP; particle ratios from PYTHIA • 3/5 PHOS geom. coverage (~ high pT limit) only Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  7. Statistics + pT Reach in 1st Pb+Pb Run • assumptions: • 3.9 TeV Pb+Pb; 5×1025 cm-2s-1; 30 days×10%; ~ 10% central (b < 5 fm) • NLO pQCD×PYTHIA ×N-N binary scaling (1,150 for central Pb+Pb) ×suppression (0.1) • 3/5 PHOS geom. coverage (~ high pT limit) only Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  8. LHC First Year versus Years at RHIC • statistics not really an issue Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  9. Technical Experiences and More • multi-photon decay channels challenging • kinematic cut optimization to improve S/B • careful combinatorial background subtraction • PHOS: highest resolution ever in RHI experiments PHENIX example wp0g PHENIX wp0g Au+Au peripheral (cent 60~92 %) 3.5 < pT < 4.5 [GeV/c] WA98 13 GeV Pb+Pb nucl-ex/0108006 PHENIX 200 GeV Au+Au run 2 ALICE 14 TeV p+p GEANT simulation after cut optimization S/√B (significance) w before cut optimization pT(w) [GeV/c] Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  10. Feasibility Evaluation Ingredients • single particle simulation • NLO pQCD×PYTHIA×N-N binary scaling×suppression • mass reconstruction in ALICE analysis framework • acceptance for multi-photon decays • two-cluster resolution (merging effect) • photon identification • 1 M central Pb+Pb HIJING at 3.9 TeV • locally generated at Hiroshima • “hybrid” approach • multiplicity effects in next steps • embedding study by combining the two h p0 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  11. S/B and S/(S+B) • better S/B, not necessarily S/(S+B), at higher pT • p0 in ~ 10% central Pb+Pb at 3.9 TeV; RAA = 0.1 • 5×1025 cm-2 s-1, 30 days, 10% uptime • feasible up to >> 10 GeV/c • more species (h, w, K0s) under study Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  12. Proof of Hybrid Approach Applicability • p0 peak visible in central Pb+Pb HIJING • consistent S/B in NLO/HIJING hybrid evaluation • multiplicity effects to be tested by embedding pT = 3 GeV/c pT = 4 GeV/c pT = 5 GeV/c pT = 6 GeV/c pT = 7 GeV/c pT = 8 GeV/c pT = 9 GeV/c pT = 10 GeV/c with gID Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  13. Summary and Concluding Remarks • new physics prospects at very high pT at LHC • ALICE at LHC starting in months (finally!) • neutral meson yields in first year very promising • both for p+p and Pb+Pb runs • real issue: S/B ratio, significance S/(S+B) • especially for multi-body decays (e.g.w, K0s) in Pb+Pb • p0 feasible even in central Pb+Pb • work in progress: h, w, K0s • solid basis on RHIC experiences • physics from very beginning of LHC operation! Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

  14. Famous Kinematic Cut: Asymmetry • discard highly asymmetric pairs to reduce BG • background concentrated at high a ( asymmetry) • acceptance only at low a at low pT • optimized for p0: a < 0.7 at pT 3 GeV/c • two photon separation only at high a at very high pT • minimum a cut option • more complicated cuts for > 2 body cases • e.g.p0–p0 energy asymmetry in K0s case Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

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