Physics in Initial Years at ALICE Kenta Shigaki, Hiroshima University (ALICE Collaboration) 30, October 2007 Workshop on Phenomenology of QGP in Heavy Ion Collisions: from SPS and RHIC to LHC at RCNP, Osaka University

LHC/ALICE/PHOS status and plans physics via photons in initial few years at ALICE  neutral mesons  pQCD photons  thermal photons ALICE/PHOS news physics at PHENIX in parallel to ALICE summary and concluding remarks Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Presentation Outline - 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Plans at LHC/ALICE - last cryo-dipole installated in August 2007 LHC start up plan  2008/04accelerator/experiments closed  2008/05beam commissioning  2008/07p+p,  s = 14 TeV, first collision  2008/endp+p,  s = 14 TeV, cm  2 s  1  soon after ?Pb+Pb,  s NN = 5.5 TeV, 5×10 25 cm  2 s  1 expectation in initial few years  p+p  s = 14 TeV, < cm  2 s  1 at ALICE  Pb+Pb  s = 5.5 TeV, cm  2 s  1, 2 – 3 years  “p”+Pb  s = 8.8 TeV, cm  2 s  1, 1 year  Ar+Ar  s = 6.3 TeV, cm  2 s  1, 1 year 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - ALICE: A Large Ion Collider Experiment - the heavy ion experiment at LHC 30 countries, 90 institutions, ~1,015 members 1000 th ALICE member 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - ALICE ≈ STAR + PHENIX - (charged particles) µ arm central barrel:  0.9 <  < 0.9  tracking and particle identification in full azimuth  partial coverage of HMPID, PHOS, EMCal forward  arm:  4 <  <  2.4 multiplicity:  3 <  < , October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - ALICE Photon Spectrometer: PHOS - photons, neutral mesons, jet tagging  + level 0 and level 1 trigger capability high resolution, high granularity   /E ~ 3 %/  E up to 100 GeV  PbWO 4 of 22 (1.0 R Moliere )×22×180 (20 X 0 ) mm 3  APD + charge sensitive preamplifier readout  temperature controlled at  25  0.1 ˚C |  | < 0.12,  = 100 degrees  56×64×5 modules 17,920 crystals, 12.5 t 30, October

- PHOS #1 (Out of 5) - waiting for installation in 2 weeks Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - ALICE/PHOS Start Up Timeline /11/12 – 14PHOS #1 installation 2007/12/02PHOS #2 ready (?) 2007/12/10 – 21magnet test 2007/12/10 – 21cosmic test run 2008/01/08 –TPC commissioning 2008/02cosmic run 2008/02/08PHOS #3 ready (?) 2008/04LHC/ALICE closed 2008/07 –physics run by 2009 ?PHOS #4, #5 installed 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Physics via Photons at LHC - vital probe of initial hot dense phase  thermal photons… temperature  thermal photon HBT… space-time evolution  direct photons… pQCD processes + jet tagging  neutral mesons… quark energy loss experimental virtues  photons and neutral mesons in same detector  particle identification to very high p t even more powerful at LHC than ever  large rates up to ~ 100 GeV 30, October thermal ~ e  E/T hadron decays jet-medium interaction jet-photon conversion bremsstrahlung pQCD processes ~ p T  n compton scattering annihilation fragmentation

- Physics Topic #1: Neutral Mesons - first piece of physics  enough acceptance with 2 – 3 PHOS modules stronger quenching and higher p t reach  clearer measurement of quark energy loss  leading to less background for direct photons Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 9 30, October 2007

- Physics Topic #2: pQCD Photons - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 10 30, October 2007 K.J.Eskola et al., NPB535 (1998) 351 F.Arleo, hep-ph/ (2006) direct photons at RHIC consistent with pQCD  consistent with simple accumulation of p+p  consistent with structure function modification  consistent with/without quenched fragmentation

- Quenched Fragmentation at LHC - pQCD photons to be suppressed significantly  another view of quark energy loss  leading to less background for thermal photons Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 11 30, October 2007 ~ 60 % suppression at 10 GeV/c F.Arleo, hep-ph/ (2007)

- Physics Topic #3: Thermal Photons - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 12 30, October 2007 indirect measurement at PHENIX  suggesting thermal component of 300 – 500 MeV high quality direct measurement at ALICE  longer life of thermalized high temperature phase  background photons suppressed due to quenching  superb PHOS detector

- Direct Photon Yield Predictions - p t direct/decaydirect/decaythermal/decaythermal/decay (GeV/c)w/o suppression80% suppressionw/o suppression80% suppression 3 [1] 4 – 10 % 4 – 10 % 3 – 9 % 3 – 9 % [2] 5 – 9 % 5 – 9 % 5 – 9 % 5 – 9 % [3] 5 – 10 % 5 – 10 % 4 – 8 % 4 – 8 % 5 [1] 6 – 12 % 12 – 25 % 3 – 9 % 6 – 18 % [2] 6 – 10 % 12 – 20 % 3 – 5 % 6 – 10 % [3] 11 – 15 % 20 – 30 % 7 – 12 % 14 – 22 % 10 [1] ~ 10 % ~ 50 % ~ 5 % ~ 25 % [2] ~ 10 % ~ 50 % < 1 % < 5 % [4] 25 – 30 % 15 – 20 % [1]F.Arleo et al., hep-ph/ [2]F.Arleo, D.d’Enterria, D.Peressounko, nucl-th/ [3]S.Turbide, R.Rapp, C.Gale, hep-ph/ [4]S.Turbide, C.Gale, S.Y.Jeon, G.D.Moore, hep-ph/ Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 13 30, October 2007

- Expectation at a Glance - predicted fraction of direct/decay photons Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 14 30, October 2007

- Limiting Factors in Photon Measurement - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 15 30, October 2007  0 p t (GeV/c) Peak extraction (%) Acceptance (%)4.0 PID efficiency (%) Energy scale linear (%) Energy scale non linear (%) Merging (%) Non vertex (%)1.5 Conversion (%)2.5 Total (%) major systematic error sources in PHENIX  conversion (uncertainty in amount of material)  off-vertex photon (uncertainty in amount of material)  acceptance (uncertainty in bad module map)  calibration and linearity  efficiency (uncertainty in reconstruction probability)  charged/neutral hadron contamination  peak extraction (uncertainty in background shape)

- Extrapolated Systematic Errors - extrapolated from PHENIX/EMC to ALICE/PHOS  based on expected PHOS performance Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 16 30, October 2007  0 p t (GeV/c) Peak extraction (%) Acceptance (%)1.0 PID efficiency (%) Energy scale linear (%)4.0 Energy scale non linear (%) Merging (%)0.0 Non vertex (%)2.0 Conversion (%)3.4 Total (%)  p t (GeV/c) Peak extraction (%) Charged contamination (%)2.4 Neutron contamination (%) Other mesons contribution (%) Acceptance (%)0.7 PID efficiency (%) Energy scale non linear (%) Merging (%)0.0 Non vertex (%)2.0 Conversion (%)1.8 Total (%)

- Potential at a Glance - expected sensitivity versus theory prediction Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 17 30, October 2007

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Thick Detectors in Front of PHOS: TRD+TOF - 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Transition Radiation Detector - tracking and particle identification  400 – 600  m resolution in r , 23 mm in z  e/  separation > 100 at p t > 3 GeV/c |  | < 0.9, full azimuth 30, October

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Time of Flight Detector - multi-gap resistive plate chamber (MRPC)  time resolution < 100 ps |  | < 0.9, full azimuth; 3.7 m from beam axis 30, October

- Material Budget Comparison - material budget in front of EM calorimeter  WA8011 %  WA – 10 %  PHENIX15 %  STAR10 %  D015 % material in front of PHOS  ITS+TPC w/o TRD+TOF20 %  ITS+TPC and TRD+TOF in technical design report40 %  ITS+TPC and TRD+TOF in current design85 % Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 21 30, October 2007

- Radiation Length Map - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 22 30, October 2007

- Problems Due to TRD/TOF Materials - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 23 30, October 2007 loss of photon statistics  factor ~ 2 for single photons significant especially in hard high p t region  leading to lower p t reach extra systematic errors  factor ~ 3 on neutral meson yield due to factor ~ 3 lower S/N ratio for photon pairs  leading to increased (major) systematic error extra background photons  factor ~ 4 of off-vertex photons  leading to increased systematic error

- Potential at another Glance - reevaluated sensitivity versus theory prediction  ~ fatal for direct photon measurement need to recover physics capability Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 24 30, October 2007

- News: Good Sign for Resolution - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 25 30, October 2007 proposal to reduce material in front of PHOS  backed up by (partly reviewed) physics arguments contributions from Hiroshima based on PHENIX experiences “holes” recommended and agreed  in 3 (out of 5) TRD+TOF modules in front of PHOS  on ALICE management board on 2007/10/04  “hole” in reality yet to be defined

Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Summary and Concluding Remarks - LHC/ALICE starting in summer, 2008  uniquely suitable for hard (and/or heavy) probes  opening new ground for “soft” photonic probes many physics via photons planned in initial years  suggestions/comments more than welcome  penetrating probes never easy to measure  material issue against PHOS being solved Hiroshima in full commitment on ALICE/PHOS  based on old (PHENIX) and new (R&D) expertise  along with still exciting physics at RHIC/PHENIX 30, October