1. 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

2. 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 2007 1

3. 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, 10 32 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, < 10 31 cm  2 s  1 at ALICE  Pb+Pb  s = 5.5 TeV, 10 27 cm  2 s  1, 2 – 3 years  “p”+Pb  s = 8.8 TeV, 10 29 cm  2 s  1, 1 year  Ar+Ar  s = 6.3 TeV, 10 29 cm  2 s  1, 1 year 30, October 2007 2

4. 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 2007 3

5. 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 <  < 5.4 30, October 2007 4

6. 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 2007 5

7. - PHOS #1 (Out of 5) - waiting for installation in 2 weeks Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 6

8. Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - ALICE/PHOS Start Up Timeline - 2007/11/12 – 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 2007 7

9. 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 2007 8 thermal ~ e  E/T hadron decays jet-medium interaction jet-photon conversion bremsstrahlung pQCD processes ~ p T  n compton scattering annihilation fragmentation

10. - 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

11. - 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/0601075 (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

12. - 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/0707.2320 (2007)

13. - 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

14. - 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/0311131 [2]F.Arleo, D.d’Enterria, D.Peressounko, nucl-th/0707.2357 [3]S.Turbide, R.Rapp, C.Gale, hep-ph/0308085 [4]S.Turbide, C.Gale, S.Y.Jeon, G.D.Moore, hep-ph/0502248 Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 13 30, October 2007

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

16. - Limiting Factors in Photon Measurement - Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 15 30, October 2007  0 p t (GeV/c) 261016 Peak extraction (%)3.72.52.42.3 Acceptance (%)4.0 PID efficiency (%)5.84.14.34.1 Energy scale linear (%)5.17.57.16.5 Energy scale non linear (%)3.51.51.05.8 Merging (%)0.0 4.8 Non vertex (%)1.5 Conversion (%)2.5 Total (%)10.510.310.012.1 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)

17. - 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) 261016 Peak extraction (%)3.72.52.42.3 Acceptance (%)1.0 PID efficiency (%)5.84.14.34.1 Energy scale linear (%)4.0 Energy scale non linear (%)1.70.70.5 Merging (%)0.0 Non vertex (%)2.0 Conversion (%)3.4 Total (%)9.17.57.87.0  p t (GeV/c) 261016 Peak extraction (%)3.72.52.42.3 Charged contamination (%)2.4 Neutron contamination (%)2.00.1 Other mesons contribution (%)6.03.0 Acceptance (%)0.7 PID efficiency (%)3.02.0 Energy scale non linear (%)1.70.70.5 Merging (%)0.0 Non vertex (%)2.0 Conversion (%)1.8 Total (%)8.95.85.7

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

19. Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop - Thick Detectors in Front of PHOS: TRD+TOF - 30, October 2007 18

20. 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 2007 19

21. 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 2007 20

22. - Material Budget Comparison - material budget in front of EM calorimeter  WA8011 %  WA98 8.5 – 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

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

24. - 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

25. - 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

26. - 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

27. 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 2007 26

28. F. Arleo et al., “Yellow Report on Photon Physics in Heavy Ion Collisions at the LHC” hep-ph/0311131 P. Aurenche, “Photon and dilepton production at LHC”, Nucl.Phys.A783:395; hep-ph/0610218 dN hadr /dy~4500 Use this calculation of decay photon yield in later estimates. Note total hadron multiplicity for further comparisons: Decay photons: hydro + NLO pQCD (no quenching) DPMJET (LO pQCD + string formation) Direct photons: hydro + NLO pQCD No suppression in central AA collisions assumed! p t (GeV) d 3 N/dyd 2 p t (no suppression) d 3 N/dyd 2 p t (suppression 0.2) 3 (2-4) 10 -1 5 (6-9) 10 -3 (2-5)10 -3 10 1 10 -4 2 10 -5 Decay photons: Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 27

29. F. Arleo et al., “Yellow Report on Photon Physics in Heavy Ion Collisions at the LHC” hep-ph/0311131 P. Aurenche, “Photon and dilepton production at LHC”, Nucl.Phys.A783:395; hep-ph/0610218 P t (GeV) N  dir /N  dec 3 (4-10) % 5 (6-12) % 10 ~10 % Ratio (total photon yield)/(decay photons): excess over 1 due to direct photons No suppression in central AA collisions assumed! P t (GeV) N  dir /N  dec 3 (4-10) % 5 (12-25) % 10 ~50 % With suppression Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 28

30. Francois Arleo, David d'Enterria, Dmitri Peressounko. “Direct photon spectra in Pb - Pb at s(NN)**(1/2) = 5.5-TeV: hydrodynamics + pQCD predictions“ Jul 2007Contributed to Workshop on Heavy Ion Collisions at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun 2007, arXiv:0707.2357 [nucl-th] Decay photons (dN hadr /dy~2000): Initial conditions of hydro corresponds to dN hadr /dy~2000 => scale properly decay photon yield from slide 1 p t (GeV) d 3 N/dyd 2 p t (no suppression) d 3 N/dyd 2 p t (suppression 0.2) 3 0.4*(2-4)10 -1 5 0.4*(6-9) 10 -3 0.4*(2-5)10 -3 10 0.4*1*10 -4 0.4*2 10 -5 p t (GeV) N  dir /N  dec (no suppression) N  dir /N  dec (suppression 0.2) 3(5-9)%(5-9)% 5(6-10)%(12-20)% 10~10%~50% Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 29

31. Hadronic Production of Thermal Photons Simon Turbide, Ralf Rapp, Charles Gale, arXiv:hep-ph/0308085 Decay photons from slide 1: p t (GeV) d 3 N/dyd 2 p t (no suppression) d 3 N/dyd 2 p t (suppression 0.2) 3 (2-4) 10 -1 5 (6-9) 10 -3 (2-5)10 -3 10 1 10 -4 2 10 -5 p t (GeV) N  dir /N  dec (no suppression) N  dir /N  dec (suppression 0.2) 3(5-10)%(5-10)% 5(11-15)%(22-30)% Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 30

32. Energy Loss of Leading Hadrons and Direct Photon production in Evolving Quark-Gluon Plasma Authors: Simon Turbide (McGill University), Charles Gale (McGill University), Sangyong Jeon (McGill University, RIKEN- BNL Research Center), Guy D. Moore (McGill University) http://arxiv.org/abs/hep-ph/0502248Simon TurbideCharles GaleSangyong JeonGuy D. Moore P t (GeV) N  dir /N  dec 10 (25-30) % Decay photons: LO pQCD (tuned to PHENIX results) + jet-thermal processes Direct photons: LO pQCD (tuned to PHENIX results) + a la hydro parameterization for thermal Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 30, October 2007 31

33. - Systematic Errors Reevaluated - systematic errors on direct photon yield in ALICE Physics in Initial Years at ALICE / K.Shigaki / RCNP Workshop 32 30, October 2007 Holes in TRD and TOFHoles in TOFNo holes p t =1.5 GeVp t =5 GeVp t =1.5 GeVp t =5 GeVp t =1.5 GeVp t =5 GeV Acceptance 2.5 Global energy scale 10  0 fit 2*8=162*4=82*8=16 3*8=32  0 ratio 2*2=42*1=22*2=4 peak extraction 2*8=162*4=83*8=24 6*8=48 efficiency 2*10=202*5=102*10=202*5=102*10=202*5=10 conversion 2*10=202*5=104*10=40 10*10=100 charged background 2*10=201*5=52.5*10=251.5*10=156*10=603*10=30 neutral background 2*10=201*5=52.5*10=251.5*10=156*10=603*10=30 Off-vertex contribution 2*10=201*5=52*10=201*10=106*10=603*10=30 Total 50%23%68%57%160 %130 %