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LHC 加速器における 高エネルギー原子核衝突実験

LHC 加速器における 高エネルギー原子核衝突実験. 志垣 賢太 （ , ALICE Collaboration ） 京都大学基礎物理学研究所研究会 “ 熱場の量子論とその応用 ” 2011 年 8 月 22 日 於 京都大学. Topicalities in Experimental Search for Hot and Dense Partonic Matter. 京都大学基礎物理学研究所研究会 「熱場の量子論とその応用」 ２００３ 年 ８ 月 ２０－２２ 日 京都大学基礎物理学研究所 志垣 賢太

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LHC 加速器における 高エネルギー原子核衝突実験

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  1. LHC 加速器における高エネルギー原子核衝突実験 志垣 賢太 （ , ALICE Collaboration） 京都大学基礎物理学研究所研究会 “熱場の量子論とその応用” 2011 年 8 月 22 日 於 京都大学

  2. Topicalities in Experimental Searchfor Hot and Dense Partonic Matter 京都大学基礎物理学研究所研究会 「熱場の量子論とその応用」 ２００３ 年 ８ 月 ２０－２２ 日 京都大学基礎物理学研究所 志垣 賢太 広島大学 / PHENIX Collaboration

  3. - Presentation Outline - • physics goals of relativistic heavy ion programs • achieved programs at BNL-RHIC • Au+Au, d+Au and p+p up to sNN = 200 GeV • hadron suppression at high pt (jet quenching) • modification of angular correlations • ongoing/near-future programs at BNL-RHIC • high statistics Au+Au (and p+p) • heavy quark states (color Debye screening) • low-mass dileptons (chiral restoration) • direct photons (thermal radiation) • more systematics with A and energy scans • future programs at CERN-LHC • strategies, expectations and ongoing activities Topicalities in Experimental Search for Hot and Dense Partonic Matter / K.Shigaki

  4. - Where are We ? What is Next ? - • quark-gluon plasma discovered ? • “it’s a quark-gluon plasma. period.” (M.Gyulassy) • maybe premature to claim triumph • further insights expected via rare processes • probe of deconfinement • heavy quark states: J/Y, Y’ • penetrating probes of medium • dileptons: e+e-, m+m- • direct photons • these measurements planned in next Au+Au run Topicalities in Experimental Search for Hot and Dense Partonic Matter / K.Shigaki

  5. - LHC Status and Plan - • accelerator on its way • startup in 2007 confirmed in June, 2003, CERN council • p+p commissioning in April 2007 • heavy ion pilot run by end of 2007 • wish list as of June 2002 • initial few years • regular p+p runs at Ös = 14 TeV, L ~ 1029 and < 31030 cm-2s-1 • 2 - 3 years of Pb+Pb at L ~ 1027 cm-2s-1 • 1 year of p/d/a+Pb at L ~ 1029 cm-2s-1 • 1 year of light ions at L ~ few 1027 - 1029 cm-2s-1 Topicalities in Experimental Search for Hot and Dense Partonic Matter / K.Shigaki

  6. - Summary and Concluding Remarks - • first round of RHIC physics programs completed • study of QCD in extreme conditions and scales • especially high energy density frontier • medium with strong final state effects formed in central Au+Au collisions • observed via jet quenching and its absence in d+Au • can be quark-gluon plasma; not conclusive yet • coming high statistics run(s) essential and exciting • additional probes of medium to be investigated • baseline established for J/Y measurement • light vector mesons also noteworthy • direct photons, unclear at SPS, to soar at RHIC/LHC • RHIC presenting rich harvest; LHC getting ready • even more fruitful physics ahead of us Topicalities in Experimental Search for Hot and Dense Partonic Matter / K.Shigaki

  7. Presentation Outline • expeditions in thermal field at LHC • QCD phase boundary crossed already at RHIC • newly started LHC/ALICE physics programs • new regime to understand deconfined partonic matter • hotter, larger, longer-lived fireball • first physics results from p+pand Pb+Pb • global properties of medium • hard and heavy probes of medium • thermometer at ALICE • summary and concluding remarks TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  8. Expeditions on QCD Phase Diagram High Energy A+A Collisions • toward deconfined partonic phase • lattice Quantum Chromo-Dynamics predictions • critical temperature ~ 170 MeV • critical energy density ~ 1 GeV/fm3 Early Universe DeconfinedPartonic Phase (Quark-Gluon Plasma) Energy Density (Temperature) Tri-Critical Point Critical Temperature ~ 170 MeV Color Super-Conductivity Hadron Gas Color-Flavor Locking F. Karsch, Lect. Notes Phys. 583 (2002) 209 Neutron Star? Nucleus Baryon Density TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  9. Where to Find “Thermometer” g q g q p p r g • thermal radiation if in equilibrium • real and virtual thermal photons • high pT: pQCD photons • low pT: photons from hadronic gas • intermediate pT: QGP thermal photons dominant ! • also other sources • plus hadron decay photons everywhere hadron decay photons S.Turbideet al., PRC 69 014903 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  10. Naïve Way: Direct Real Photons • measured as “excess” above hadron decay photon • Au+Au result consistent with pQCD×binary scaling • challenging at lower pT due to smaller S/B ratio PRL 94, 232301 (2005) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  11. Alternative: “Almost Real” Photons • low mass electron-positron pairs • p+p: hadronic decay + pQCD photon at high pT • Au+Au: enhancement above ~ 135 MeV • no p0 decay virtual photon above p0 mass PHENIX (A. Adareet al.), PRL 104, 132301 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  12. Direct Photon Spectra via g and g* • real and virtual photon methods consisitent • p+p data consistent with pQCD down to low pT • Au+Au above scaled pQCD at low pT • excess ~ exponential with 221  19  19 MeV PHENIX (A. Adareet al.), PRL 104, 132301 (2010) NLO pQCD (W. Vogelsang) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  13. Initial Temperature Evaluation • initial temperature > data slope ~ 220 MeV • 300–600 MeV from models • hydro-dynamical models describing data within factor of 2 • w/ t0 = 0.15–0.6 fm/c • cf. phase transition predicted at ~ 170 MeV slope transition temperature PHENIX (A. Adareet al.), PRC 81, 034911 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  14. Across the Boundary and Beyond • phase boundary: Tc ~ 170 MeV, ec ~ 1 GeV/fm3 “free gas” ? RHIC “perfect fluid” RHIC TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  15. ALarge Ion Collider Experiment • the heavy ion experiment at LHC • 33 countries; 116 institutes; > 1,000 members • as of November, 2010 CMS LHCb ALICE ATLAS, LHCf TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  16. LHCRun History and Plan • LHC run history and schedule • 2009 p+p at s = 900 GeV, 2.36 TeV • 2010–2012 p+p at s = 7 TeV (and 2.76 TeV) Pb+Pb at sNN = 2.76 TeV • 2014 full design energy • expectations in following few years • p+ps = 14 TeV, 1031 cm-2s-1 (ALICE), 107 s/y s = 5.5 TeV, 1031 cm-2s-1, 106 s/y×1 y • Pb+PbsNN = 5.5 TeV, 1027 cm-2s-1, 106 s/y • p+Pb sNN = 8.8 TeV, 1029 cm-2s-1, 106 s/y×1 y • Ar+Ar sNN = 6.3 TeV, 1029 cm-2s-1, 106 s/y×1 y TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  17. The Highest Baseline, 7 TeV p+p • ALICE 2010 p+p data taking • > 800 M interactions • > 100 M muon triggers for J/Y • > 25 M high multiplicity triggers TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  18. Almost Zero Baryo-Chemical Potential • anti-proton/proton ratio in mid-rapidity region • 0.957  0.006 (stat)  0.014 (sys) at 900 GeV • 0.990  0.006 (stat)  0.014 (sys) at 7 TeV ALICE (K. Aamodtet al.), PRL 105, 072002 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  19. Vital Reference in New Energy Domain • e.g. closed/open heavy flavors • J/Y, D0, D, D J/Y m+m- J/Y e+e- TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  20. First Pb+Pb Run in Late 2010 • 2.76 TeV Pb+Pb from 07.11.2010–06.12.2010 • 14 times higher sNN than at RHIC TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  21. ALICE 2010 Pb+Pb Data Taking • ~ 10 mb-1 delivered; > 90 M recorded in total • 3% of nominal luminosity (1027 cm-2s-1) at end of run • ~ 3×initial expectation TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  22. ATLAS, CMS Having Fun, Too • first physics results within a few weeks into run TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  23. Charged Particle Multiplicity Density • dNch/dh = 1580  80 (sys) • high side of predictions • faster growth with s than in p+p • i.e. s dependent nuclear amplification ALICE (K. Aamodtet al.), PRL 106, 032301 (2011) back at RHIC TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  24. Initial Energy Density • ~ 2.5×transverse energy density than at RHIC • from Bjorken formula: • et0 ~ 16 GeV/fm2c ~ 3×at RHIC • lower limit for e; likely higher with shorter time scale TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  25. Hotter, Larger, Longer-Lived Fireball Enhancement p+p 7 TeV radius ~ 1/width Pb+Pb 2.76 TeV Pair Momentum Difference • Bose Einstein (aka HBT) particle interferometry • space-time evolution of co-moving volume • lifetime also accessible via Fourier transformation (E, p)  (t, x) • particle multiplicity dependences consistent with models • ~ 2×larger, 20–30% long-lived than at RHIC • ~ 300 fm3, ~ 10 fm/c ALICE (K. Aamodtet al.), PLB 696, 328 (2011) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  26. Still Strongly Coupled (as at RHIC)? • strongly coupled medium found at RHIC • large elliptic azimuthal anisotropy (v2) • pT averaged v2 increase by 30% at LHC ALICE (K. Aamodtet al.), PRL 105, 252302 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  27. pT Differential Azimuthal Anisotropy • consistent at LHC and RHIC within uncertainties • sNN = 2.76 TeV and 200 GeV • 30% increase explained by higher mean pT • higher freeze out temperature? • stronger collective radial expansion? ALICE (K. Aamodtet al.), PRL 105, 252302 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  28. Collective Radial Expansion • mean pT rise, especially for heavier particles • no scaling behavior with particle multiplicity density • smooth kinematic connection assuming blast wave • superposition of thermal emission + radial expansion • stronger radial expansion at LHC p, K, p common blast wave fit TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  29. Powerful Hard/Heavy Probes at LHC • much harder and abundant jets than at RHIC • ~ 10×charming and ~ 100×beautiful than at RHIC • powerful probes with known mass and color charge charm/beauty sNN (mb) shadowing multiplicity • p+p 14 TeV 11.2/0.5 1.0/1.0 0.16/0.007 • central Pb+Pb 6.6/0.2 0.65/0.85 115/4.6 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  30. Jet Quenching and Mono-Jet Df Dh Dh Df • quark/gluon energy loss in partonic matter • first signature of hot and dense matter at RHIC • jet energy imbalance in single events • new at LHC! • full statistics analysis in progress • ALICE uniquely capable to include low pT particles high pT hadron quenched jet hadrons (jet) quark (anti-)quark hadrons (jet) high pT hadron TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  31. Ev.-by-Ev. Di-Jet Asymmetry (ATLAS) • full jet reconstruction with anti-kT clustering • energy asymmetry • asymmetric jets in central collisions see also ATLAS (G. Aadet al.), PRL 105, 252303 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  32. Ev.-by-Ev. Di-Jet Asymmetry (CMS) • full jet reconstruction with iterative cone clustering CMS (S. Chatrchyanet al.), arXiv:1102.1957 [nucl-ex] (2011) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  33. Jets (Quenched but) Barely Modified • angular correlation maintained • fragmentation as in vacuum CMS-PAS-HIN-11-004 see also ATLAS (G. Aadet al.), PRL 105, 252303 (2010) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  34. Energy Widely Re-Distributed (CMS) • consistent with picture of: • strong out-of-cone energy loss • remnant parton fragmentation in vacuum CMS (S. Chatrchyanet al.), arXiv:1102.1957 [nucl-ex] (2011) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  35. Singles to Probe Quark Energy Loss normalization including CDF data normalization by 0.9 TeV ×NLO (2.76 TeV) / NLO (0.9 TeV) • particle yields suppressed at high pT • quantified with “nuclear modification factor” • similar overall trend at LHC and RHIC • minimum value ~1.5 times smaller • rising with pT; newly clear at LHC • 2.76 TeV p+p reference collected in 2011 ALICE (K. Aamodtet al.), PLB 696, 30 (2011) LHC-ALICE charged particles RHIC-PHENIX p0 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  36. Colorless Reference (CMS) • direct prompt photon expecting no suppression • identified with isolation and shower shape • no nuclear modification seen CMS-PAS-HIN-11-002 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  37. Inclusive Charged Hadron RAA preliminary • maximum suppression by factor ~ 7 at ~ 7 GeV/c CMS-PAS-HIN-10-005 see also ALICE (K. Aamodtet al.), PLB 696, 30 (2011) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  38. Jet Yield Suppression (ATLAS) • central/peripheral ratio ~ 0.5 • consistent with single particle suppression R = 0.4 R = 0.2 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  39. Identified Hadron Suppression • baryon/meson difference as at RHIC • still vital probe for parton energy loss systematics , 0 K0s,  TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  40. Open Charm Suppression • charm behaving similarly with lighter quarks • systematic measurements and theory comparison • gluon/quark; Casimir factors? • light/heavy; dead cone effect? D+ TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  41. Heavy Flavor via High pT Leptons • accessible to charm and beauty energy loss • higher pT leptons mainly from beauty • beauty also strongly suppressed? TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  42. Beauty Quark Quenching (CMS) • non prompt (off vertex) J/Y from B decay • prompt and non prompt J/Y suppressed at high pT • potential discretion between charm and beauty CMS-PAS-HIN-10-006 TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  43. Closed Heavy Flavor Suppression • J/Y suppression as a signature of deconfinement • observed at RHIC and SPS; interpretation ambiguous •  and its sub-states key to resolve mechanism • competing mechanisms • melting, recombination, feed down, … TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  44. J/ Suppression at LHC • J/ RAA at 2.76 TeV and 0.2 TeV • always note kinematic differences • (pseudo-)rapidities, transverse momentum ranges TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  45. Higher  States Suppression (CMS) • higher resonances expected to melt earlier • (1s) suppressed by 0.6  0.15 • (2s, 3s) further suppressed; 2.4s effect CMS-PAS-HIN-10-006 CMS-PAS-HIN-11-007 CMS (S. Chatrchyan et al.), arXiv:1105.4894 [nucl-ex] (2011) TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  46. More Fun Stuffs, Too • e.g. anti-nuclei • … and even more exotics, e.g. anti-hyper-nuclei ~ 2 M minimum-bias Pb+Pb TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  47. Thermal Photon Hunting at ALICE • 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 • s/E ~ 3 %/E up to 100 GeV • PbWO4 crystals of 22 (1.0 RMoliere)×22×180 (20 X0) mm3 • APD+ charge sensitive pre-amplifier readout • cooled and controlled at -250.1 C • |h| < 0.12, Df = 100 at 4.6 m • 56×64×5 modules; 17,920 channels, 12.5 t • 3 (/5) modules in operation hadron decays pQCD processes ~ pT-n compton scattering annihilation fragmentation thermal ~ e-E/T jet-medium interaction jet-photon conversion bremsstrahlung TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  48. Summary and Concluding Remarks • nuclear physics program at LHC now in full glory • hotter, larger, longer-lived fireball than at RHIC • ~ 3 (or more)  higher initial energy density • ~ 2  larger and 20–30% longer lived at freeze out • smooth kinematic connection of soft observables • surprises and theory challenges in hard probes • hadron spectra further modified • heavy quark similarly suppressed at higher pT • first direct measurements of beauty and  suppression • strong di-jet energy imbalance and out-of-cone radiation • regime to understand deconfined partonic matter! TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

  49. Final Notes and Acknowledgement • symposium at JPS fall 2011 in Hirosaki • session 17pSJ: 9/17 (Sat.) afternoon • followed by QCD matter open forum informal meeting • WPCF’11 (Hongo, Tokyo, 9/20–24) • ISMD’11 (Miyajima, Hiroshima, 9/26–30) • special thanks to A. Morsch (ALICE) • many slides inspired by his PLHC’11 presentation TQFT’11 – High Energy Nuclear Collision Experiments at LHC – K.Shigaki

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