Photon Analysis Strategies at ALICE Kenta Shigaki (Hiroshima University ) ALICE Asian Workshop November 5, 2009 Yonsei University, Seoul

physics prospects at ALICE/LHC –physics outcomes (and standing issues) at RHIC –global understanding of new state of matter importance of photons in wide p T range physics via photons – goals, prospects, status –neutral mesons, pQCD photons, thermal photons first year physics strategies data import strategy summary and concluding remarks Presentation Outline Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 1/21

dense: energy loss of (even heavy) quarks –jet quenching (high p T suppression) –jet modification partonic: quarks’ degrees of freedom, screening –constituent quark number scaling of collective motion –J/  suppression strongly coupled: perfect fluidity –hydro-dynamical collective motion hot: thermally radiative –thermal (virtual) photons RHIC Outcomes: New State of Matter Nov. 5, 2009 The matter may melt and/or regenerate J/  ’s The matter is dense The matter modifies jets The matter is hot The matter is strongly coupled ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 2/21

partonic density –jet quenching/modification at very high p T –J/ ,  suppression/regeneration initial temperature and space-time evolution –thermal photons –thermal photon correlation chiral symmetry restoration –mass states of light vector mesons i.e. global understanding via penetrating probes LHC to overcome physics issues Standing Issues to Overcome Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 3/21

Photon Collection from HI Collisions Nov. 5, 2009 Pre-equilibrium Thermalization QGP phase? Mixed phase Hadronization (Freeze-out) + Expansion Compton/Annihillation Fragmentation Prompt Photon Jet-Photon Conversion Jet-Bremsstrahlung (QGP) Jet+Medium Thermal Photon (QGP) Thermal Photon (HG) Thermal Photon ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 4/21

ALICE photon spectrometer: PHOS –photons, nuetral mesons, jet tagging + L0, L1 trigger capability wide coverage from 100 MeV to 100 GeV –high eneregy resolution, high granularity  /E ~ 3 %/  E [GeV] up to 100 GeV PbWO 4 crystals of 22 (1.0 R Moliere )×22×180 (20 X 0 ) mm 3 APD + charge sensitive pre-amplifier readout cooled and controlled at  25  0.1  C –|  | < 0.12,  = 100  at 4.6 m 56×64×5 modules; 17,920 channels, 12.5 t –3 (out of 5) modules installed and cooled Precise Photon Measurement at ALICE Nov. 5, 2009 thermal ~ e  E/T hadron decays jet-medium interaction jet-photon conversion bremsstrahlung pQCD processes ~ p T  n compton scattering annihilation fragmentation ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 5/21

LHC start-up schedule –2008/09first beam –2009/12p+p,  s = 0.9, 2.2 TeV –2010p+p,  s = 10 TeV, cm  2 s  1 –2010/10Pb+Pb,  s NN = 3.9 TeV, 5×10 25 cm  2 s  1 expectations in initial years –p+p  s = 14 TeV, cm  2 s  1 (ALICE), 10 7 s/y  s = 5.5 TeV, cm  2 s  1, 10 6 s/y×1 y –Pb+Pb  s NN = 5.5 TeV, cm  2 s  1, 10 6 s/y –p+Pb  s NN = 8.8 TeV, cm  2 s  1, 10 6 s/y×1 y –Ar+Ar  s NN = 6.3 TeV, cm  2 s  1, 10 6 s/y×1 y Boundary Condition: LHC Schedule Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 6/21

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 Physics #1: Neutral Meson Quenching Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 7/21

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 Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 8/21

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 Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 9/21

statistics not really an issue LHC First Year versus Years at RHIC Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 10/21

Real Feasibility Issue: Significance Nov. 5, 2009 single particle + HIJING “hybrid” approach –NLO pQCD×PYTHIA×N-N binary scaling×suppression –mass reconstruction in AliRoot e.g.  0 in ~ 10% central Pb+Pb at 3.9 TeV –5×10 25 cm -2 s -1, 30 days, 10% uptime; R AA = 0.1 for details, ref. H.Torii, this afternoon for multiplicity effect studies, ref. H.Sakaguchi, Saturday ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 11/21

direct photon universality in p+p and p+p –also pQCD prediction –good probe of PDF possibly new physics in any enhancement Physics #2: p+p (p+p) Universality Nov. 5, 2009 Preliminary ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 12/21

direct photon at RHIC: consistent with pQCD –consistent with simple p+p superposition –consistent w/ and w/o nuclear modification of PDF –consistent w/ and w/o string fragmentation quenching hard photons at ALICE/LHC –# prompt photons ~ # decay photons at > 60 GeV –large rate up to very high p T Physics #3: pQCD Photon in A+A Nov. 5, 2009 K.J.Eskola et al., NPB535 (1998) 351 F.Arleo, hep-ph/ (2006) ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 13/21

significant suppression of pQCD photons expected –independent measurement of quark energy loss –less background for thermal photon measurement Quenched String Fragmentation Nov. 5, 2009 ~ 60 % suppression at 10 GeV/c F.Arleo, hep-ph/ (2007) ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 14/21

unique probe of central part of hot matter ref. H.Z.Zhang, this afternoon ref. Y.Miake, earlier in this session H.Z.Zhang et al. PRL98(2007) slides at ATHIC08 Physics #4: Transparent Hard Tagging Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki single hadron di-hadron gamma-hadron small z T 15/21

quark jet identification via associated photon –gluon jet naively quenched more than quark jet test of quenching mechanism –high p T photon/  0 separation essential Quark/Gluon Jet Identification Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki single  0 PYTHIA 14 TeV di-jet PYTHIA 5.5 TeV gamma-jet PYTHIA 5.5 TeV quark jet gluon jet quark jet gluon jet 16/21

Photon Physics #5: Thermal Photons Nov. 5, 2009 RHIC outcome –radiation at 300 – 500 MeV (!) implied indirect measurement via  * cf. critical temperature ~ 170 MeV –models not strongly constrained LHC prospect –direct measurement of thermal photons higher temperature + longer life time reduced background due to quenching ALICE-PHOS detector –understanding of thermal properties of partonic system ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 17/21

Direct/Thermal Photon Feasibility Nov. 5, 2009 expected signal/background ratio –4 ~ 10 % (3 GeV/c) – 25 ~ 50 % (10 GeV/c) expected systematic error with PHOS –8.9 % (2 GeV/c) – 5.7 % (10 GeV/c) detailed study still needed ref. H.Torii, this afternoon ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 18/21

2010/02: p+p particle production – first paper –(low p T ) neutral mesons taskforce in PWG4; co-convener H.Torii T.Iwasaki 2010/08: p+p baseline for Pb+Pb –p+p high statistics neutral mesons (and direct photons) H.Torii + grad. students 2011/02: Pb+Pb quark energy loss –Pb+Pb neutral mesons K.Shigaki + grad. students 2011/06: Pb+Pb thermo-dynamics –Pb+Pb direct/thermal photons First Year Physics Strategies Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 19/21

ALICE data rate expectation –triggered data 2.5 PB/yr –event summary data (ESD)~ 600 TB/yr –analysis object data (AOD) ~ 60 TB/yr at least PWG4 AOD (~ 15 TB/yr ?) to Hiroshima T2 –~ 4 Mbps full time in average; feasible –need to keep AOD updated; frequency unknown all AOD in Asia desirable? –Hiroshima + KISTI ? massive ESD import unrealistic –any use of sampled ESD? Data Import Strategy (for Discussion) Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 20/21

physics prospects at LHC after RHIC discoveries –global understanding of hot partonic matter –ALICE at LHC starting in months (finally!) key analyses: photons in very wide p T range –high p T neutral mesons and direct/thermal photons –both in p+p and Pb+Pb ultimate challenge: low/int. p T thermal photons in Pb+Pb analysis strategies laid out; need to materialize! data import strategy discussions being called goal: photon physics from very beginning of LHC! Summary and Concluding Remarks Nov. 5, 2009 ALICE Asian Workshop – Photon Analysis Strategies at ALICE – K.Shigaki 21/21