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

+ all PHOS and PWG4 (jet/photon) collaborators Most Relevant Members 1/12Oct.14, 2009 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki Kenta Shigaki Aya Hiei Hisa Torii

LHC/ALICE/PHOS status and schedule high p T neutral mesons in first year of ALICE –statistics and p T reach –technical challenges and resolutions first high p T physics prospects –  0 in Pb+Pb run in 2010 –more work in progress summary and concluding remarks Presentation Outline Oct.14, 20092/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

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 LHC/ALICE/PHOS Status & Schedule 3/12Oct.14, 2009 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki September, 2009 Pb beam injection oriented

Jet Quenching at LHC Oct.14, 20094/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki higher p T 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

assumptions: –10 TeV p+p; 5×10 28 cm  2 s  1 ; 180 days×10% –  0 in NLO/CTEQ6M/KKP; particle ratios from PYTHIA –3/5 PHOS geom. coverage (~ high p T limit) only Statistics + p T Reach in 1 st p+p Run Oct.14, 20095/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

assumptions: –3.9 TeV Pb+Pb; 5×10 25 cm  2 s  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 p T limit) only Statistics + p T Reach in 1 st Pb+Pb Run Oct.14, 20096/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

statistics not really an issue LHC First Year versus Years at RHIC 7/12Oct.14, 2009 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

Technical Experiencesand 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    0  Au+Au peripheral (cent 60~92 %) 3.5 < pT < 4.5 [GeV/c ] p T (  ) [GeV/c] S/√B (significance) before cut optimization after cut optimization  PHENIX example    0  Oct.14, 20098/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki WA98 13 GeV Pb+Pb nucl-ex/ PHENIX 200 GeV Au+Au run 2 ALICE 14 TeV p+p GEANT simulation

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 Feasibility Evaluation Ingredients 00  Oct.14, 20099/12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

better S/B, not necessarily S/  (S+B), at higher p T  0 in ~ 10% central Pb+Pb at 3.9 TeV; R AA = 0.1 5×10 25 cm -2 s -1, 30 days, 10% uptime feasible up to >> 10 GeV/c more species ( , , K 0 s ) under study S/B and S/  (S+B) Oct.14, /12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

 0 peak visible in central Pb+Pb HIJING consistent S/B in NLO/HIJING hybrid evaluation –multiplicity effects to be tested by embedding Proof of Hybrid Approach Applicability p T = 3 GeV/cp T = 4 GeV/cp T = 5 GeV/c p T = 6 GeV/cp T = 7 GeV/cp T = 8 GeV/c p T = 9 GeV/cp T = 10 GeV/c Oct.14, /12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki with  ID

new physics prospects at very high p T 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. , K 0 s ) in Pb+Pb  0 feasible even in central Pb+Pb work in progress: , , K 0 s –solid basis on RHIC experiences physics from very beginning of LHC operation! Summary and Concluding Remarks Oct.14, /12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki

discard highly asymmetric pairs to reduce BG –background concentrated at high  (  asymmetry) –acceptance only at low  at low p T –optimized for  0 :  < 0.7 at p T  3 GeV/c –two photon separation only at high  at very high p T minimum  cut option more complicated cuts for > 2 body cases –e.g.  0 –  0 energy asymmetry in K 0 s case Famous Kinematic Cut: Asymmetry Oct.14, /12 Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki