September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 1 First Physics with ALICE at LHC Cai Xu and Zhou Daicui Institute of Particle Physics Central China Normal University The first beam in the Large Hadron Collider at CERN

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 年 9 月 10 日， LHC 正式启动，粒子束流首次试运行 Physics of the LHC 暗物质暗能量 夸克物质 空间额外维度 反物质黑洞 质量起源

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 年 9 月, 斯蒂芬 霍金访问 CERN 时，参观 LHC 隧道 2008 年 4 月，彼特 希格斯出席 LHC 开放日时, 参观 LHC 隧道内的实验室 2007 年 1 月，杨振宁访问 CERN 时， 参观 LHC 隧道内 CMS 实验室 2007 年 8 月，李政道访问 CERN 时， 参观 LHC 隧道内 ATLAS 实验室 2007 年 2 月, 乔治 斯穆特访问 CERN 时，参观 LHC 隧道内的实验室 2007 年 1 月, 格拉德﹒特霍夫特访问 CERN 时, 参观 LHC 隧道内的实验室

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 4 * L max (ALICE) = ** ∫ L dt (ALICE) ~ 0.7 nb -1 /year Collision system pp PbPb √s NN (TeV) L 0 (cm -2 s -1 ) /L 0 (%) Run time (s/year) σ inel (b) * * * 7.7 LHC as Ion Collider Running conditions for ‘typical’ Alice year: other collision systems: pA, lighter ions (Sn, Kr, Ar, O)

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 5 From RHIC to LHC s cc → ~ 1 s bb → ~ 100 s jet>100GeV → ~ ∞ s RHIC (  → l l ) ~ s LHC (Z → l l ) Cross sections at LHC

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 6 From RHIC to LHC x min  ~ – factor 1/30 due to energy – factor 1/3 larger rapidity With J/ψ at rapidity 4 – Pb-Pb collisions x min ~ – pp collisions x min ~ 3×10 -6 New low-x regime at LHC

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 7 From RHIC to LHC e 0 = dN/dy /t 0 4pR 2 – increase by factor 2–3 QGP lifetime – increase by factor 2–3 Energy density at LHC

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 8 > 1000Members (63% from CERN MS) ~ 30Countries ~ 100Institutes ALICE : collaboration of nuclear and particle physicists with strong engineering and industrial participation ALICE Collaboration

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 9 Size: 16 x 26 meters Weight: 10,000 tonnes ALICE: A Large Ion Collider Experiment at CERN-LHC

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 10 complete – fully installed & commissioned  ITS, TPC, TOF, HMPID, MUONS, PMD  V0, T0, FMD, ZDC, ACORDE, DAQ partially completed  TRD (25%) to be completed by 2009  PHOS (60%) 2010  HLT (30%) 2009  EMCAL (0%) 2010/11 at start-up full hadron and muon capabilities partial electron and photon capabilities Start-up configuration 2008

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 11 L3 magnet TPC Central part of ALICE ITS HMPID

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 12 Robust, redundant tracking from 100 GeV/c Very little dependence on dN/dy (up to dN/dy ≈ 8000) ALICE Tracking Performance  p/p < 5% at 100 GeV with careful control of systematics dN ch /dy=6000 drop due to proton absorption TPC acceptance = 90% Momentum resolution ~ 100 GeV

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 13 ‘stable’ hadrons (π, K, p): 100 MeV/c < p < 5 GeV/c; (π and p with ~ 80 % purity to ~ 60 GeV/c) dE/dx in silicon (ITS) and gas (TPC) + time-of-flight (TOF) + Cherenkov (RICH) decay topologies (K 0, K +, K -, Λ, D) K and L decays beyond 10 GeV/c leptons (e,μ ), photons, π 0 electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π 0 in PHOS: 1 < p < 80 GeV/c excellent particle ID up to ~ 50 to 60 GeV/c Particle Identification in ALICE

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理  X/X 0 CMS outer/inner silicon ATLAS TRT/SCT ALICE TPC/ITS Ultimate cut-off – the amount of material in the tracker (ALICE compared to other LHC detectors) relatively low magnetic field Low momentum cut-off

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 15 First pp run (starting September 2008 )  important pp reference data for heavy ions  minimum bias running  unique pp physics with ALICE Early heavy-ion run (10 6 1/20 nominal luminosity in 2009)  establish global event characteristics  bulk properties (thermodynamics, hydrodynamics… )  start of hard probe measurements First Physics with ALICE from pp to Pb–Pb

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 16 pp Physics with ALICE ALICE detector performs very well in pp ○ very low-momentum cutoff (<100 MeV/c) new x T - regime (down to 4×10^ (-6) ) ○ p t - reach up to 100 GeV/c ○ excellent particle identification ○ efficient minimum-bias trigger ○additional triggers First physics in ALICE will be pp ○ provides important reference data for heavy-ion programme Unique pp physics in ALICE e.g. ○ multiplicity distribution ○ baryon transport ○ measurement of charm cross section major input to pp QCD physics Start-up ○ some collisions at 900 GeV  connect to existing systematics pp nominal run ○ ∫Ldt = 3·10^ (30) cm ^ (-2) s^ (-1) × 10^ (7) s 30 pb-1 for pp run at 14 TeV Npp collisions = 2·10^ (12) collisions ○ minimum-bias triggers: 20 events pile-up (TPC) Npp minb = 10^ (9) collisions ○ high-multiplicity trigger: reserved bandwidth ~ 10Hz ○ muon triggers: ~ 100% efficiency, < 1kHz ○ electron trigger: ~ 25% efficiency of TRD L1

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 17 ○ operating with fast multiplicity trigger L0 from Silicon Pixels ○ efficiency studied for - single diffractive events - double diffractive events - non-diffractive events Charged Particle Acceptance

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 18 LHC  extend existing energy dependence  unique SPD trigger (L0) for minimum-bias precision measurement  completely new look at fluctuations in pp (neg. binomials, KNO…) trigger efficiency ND-INEL 98% SD 55% DD 58% Charged Particle Multiplicity

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 19 Silicon Pixel Detector (clusters/tracklets) Initial multiplicity reach Energy density in high-multiplicity pp events (Bjorken formula) – dN/dy few (2–4) 102 smaller – increase ~ 30 (smaller size)  at 10 times the mean multiplicity energy density as with heavy ions with 20k minimum bias pp events up to multiplicity ~ 8 times the average (30 events beyond) multiplicity trigger to enrich the high-multiplicity

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 20 MB + 3 triggers 250 kHz coll. rate Bins < 5 entries removed High-multiplicity trigger Example of threshold tuning: MB and 3 high-mult. triggers 250 kHz collision rate recording rate 100 Hz MB 60% 3 HM triggers: 40% Cut fired chips Fired chips vs. true multiplicity (in  of layer) multiplicity in layer

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 21 Baryons in central region at LHC at LHC – 9.61 ← η H1 (HERA) Δη ~ 7 systematics due to beam-gas Interactions will be easier at LHC

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 22  +,proton  -,antiproton  systematic error of asymmetry below 1% for p > 0.5 GeV/c: contributions from uncertainties in the cross sections, material budget, beam gas events  statistical error < 1% for 10 6 pp events (< 1 day)  additional prediction asymmetry increases with multiplicity  will be extended to   (asymmetry larger) Asymmetry measurement ASYMMETRY

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 23  with 20k events we reach (first few days) 5 GeV (at 0.9 TeV) 10 GeV (at 14 TeV)  with O(10 8 ) events we reach (first month ) 15 GeV (at 0.9 TeV) 50 GeV (at 14 TeV) Initial transverse momentum reach

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 24 Reach up to 12 – 14 GeV/c with 5 – 10×10 7 events 30% D 0  K + π for 10 9 pp events Heavy-flavour physics

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 25 Fully commissioned detector & trigger ○ alignment, calibration available from pp First 10 5 events: global event properties ○ multiplicity, rapidity density ○ elliptic flow First 10 6 events: source characteristics ○ particle spectra, resonances ○ differential flow analysis ○ interferometry First 10 7 events: high p t, heavy flavours ○ jet quenching, heavy-flavour energy loss ○ charmonium production Yield bulk properties of created medium ○ energy density, temperature, pressure ○ heat capacity/entropy, viscosity, sound velocity, opacity ○ susceptibilities, order of phase transition Early ion scheme ○ 1/20 of nominal luminosity ○ ∫Ldt = 5·10 25 cm -2 s -1 x 10 6 s 0.05 nb -1 for PbPb at 5.5 TeV N pp collisions = 2·10 8 collisions 400 Hz minimum-bias rate 20 Hz central (5%) ○ muon triggers: ~ 100% efficiency, < 1kHz ○ centrality triggers: bandwidth limited N Pb Pbminb = 10 7 events (10Hz) N PbPbcentral = 10 7 events (10Hz) Heavy-ion physics with ALICE

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 26 integrated multiplicity distributions from Au-Au/Pb-Pb collisions and scaled pp collisions ALICE designed (before RHIC) for dN ch /dy = 3500 design checked up to dN ch /dy = 7000 dN ch /dy = 2600 dN ch /dy = 1200 J. Phys. G 30 (2004) 1540 ln(√s) extrapolation saturation model Eskola hep-ph/ Charged-particle Multiplicity Density

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 27 with part of the event removed displaced vertices can be seen Tracking Challenge

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 28 4 Silicon Pixel Detector: -1.6 < η < +1.6 Forward Multiplicity Detectors: η → -5, +3.5 First estimate of energy density Saturation, CGC ? dN/dη % centrality (N part ) Fraction of particles produced in hard processes Central Hijing event Global event properties in Pb-Pb Multiplicity distribution (dN ch /dη) in Pb-Pb

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 29 Elliptical Flow - Day 1 Physics AGS SPS RHIC event plane resolution < 10º very robust signal - no PID necessary reaction plane X Z Y LHC ● data increase linearly ● hydrodynamical limit reached at RHIC  ‘ideal fluid’ ● clear predictions from hydrodynamics ● sensitive to equation-of-state

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 30 Standard event-plane method 500 HIJING event centrality b = 8fm multiplicity = 1900 integrated v 2 = 3.3% Lee-Yang Zero method 1100 HIJING event centrality b = 9fm multiplicity = 1200 integrated v 2 = 6% red – modified LYZ method (J-Y Ollitrault) v 2 measurement studies

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 31 5 Excitation functions of bulk observables for identified hadrons New regime at LHC: strong influence of hard processes Chemical composition Equilibrium vs non equilibrium stat. models ? Jet propagation vs thermalization ? Strangeness production : correlation volume (N part → GC, N bin → hard processes) ? Interplay between hard and soft processes at intermediate p T Parton recombination + fragmentation ? Soft (hydro -> flow) + quenching ? → R cp : central over peripheral yields / 〈 N bin 〉 → Baryon/meson ratio → Elliptic flow RHIC Identified particle spectra in Pb-Pb

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 32 7 Statistical limit : p T ~ GeV for K +, K -, K 0 s, Λ Reconst. rates: X: 0.1/event W: 0.01/event p T : 1 to 3-6 GeV Pb-Pb central 13 recons.  /event  300 Hijing events 8-10 GeV Topological identification of strange particles (1)

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 33  300 central events 13  /evt 10 7 events: p t reach , K,  ~ GeV; p t reach    ~ 9-12 GeV           central Pb-Pb Mass resolution ~ 2-3 MeV  → K + K - Mass resolution ~ 1.2 MeV hadrochemical analysis chemical/kinetic freeze-out medium modifications of mass, widths Topological identification of strange particles (2) Thermal Freeze out Nuclear matter

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 Two pion momentum correlation analysis event mixing, two track resolutions, track splitting/merging, pair purity, Coulomb interactions, momentum resolution corrections, PID corrections Central Pb-Pb events (0-2 fm) with dN/dy = 6000 R simul. (fm) R rec (fm) Other potential analyses Two kaon & two proton correlations Single event HBT Direct photon HBT, … Correlations fonctions C(q long ) C(q out ) C(q side ) q (GeV/c) C(q inv ) q inv (GeV/c) Particle correlations

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 35 Fluctuations are associated with phase transition Event-by-event fluctuations at LHC easier, due to increased event multiplicity complication, a large mini-jet production, T, multiplicity, particle ratio, strangeness, azimuthal anisotropy, long range correlations, balance function, …  Resolution  T /T: 0.5 % for  4 th moment of the net charge Lattice computations at small chemical potential Event-by-Event Fluctuations

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 36 High precision vertexing, s~100 mm (ITS) High precision tracking (ITS+TPC+TRD) K and/or p identification (TOF) Overall significance for 10 6 events ~10 High precision open charm measurement 1<p T <2 GeV/c 10 times lower statistics ~factor 3 in the significance, we can measure D 0 in the pilot run D0  Kπ channel

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 37 stat error stat syst error 11% from overall normalization not included 10 7 events (full TRD) statistical. systematic. with 10 7 events Acceptance down to very low p t Heavy-quarks and quarkonia bottom charm LHCRHICSPS N(qq) per central PbPb collision

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 38 Probes colour charge dependenceProbes mass dependence One year at nominal luminosity: 10 9 pp events; 10 7 central PbPb events Heavy-flavour quenching: R AA

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 39 J/Ψ ~ 3*10 5 Υ ~ 8000 Di-muon mass spectrum One month (10^6 sec) Pb-Pb collisions at nominal luminosity Adequate statistics to study Υ- family and quench-scenarios

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 40 J/Ψ ~ 3*10 5 Suppression vs recombination Υ ~ 8000 Quarkonia production

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 GeV GeV 1.5  GeV 5  GeV N jets E T threshold 10 6 central PbPb collisions ALICE Acceptance events 10 6 central Pb-Pb events (pilot run) Jet statistics in pilot Pb run

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 accepted jets/month jets/event Pb+Pb p t jet > (GeV/c) Jet Production at LHC ● Initial measurements up to 100 GeV (untriggered charged jets only) ● Detailed study of fragmentation possible ● Sensitive to energy loss mechanism ● Accuracy on transport coefficient ~20%

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 43  all /  dec Thermal and hard photons

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 44 pp  R = 0.3, Sp T < 2 GeV/c  Efficiency: 69%  Background rejection: 1/170  First year (10 pb -1 )  3000 g (Eg > 20 GeV) PbPb  R = 0.2, p T thresh = 2 GeV/c  Efficiency: 50%  Background rejection: 1/14  One month of running  2000 g (E g > 20 GeV)  Increases to 40 GeV with EMCal  5 5 signal Identifying prompt γ in ALICE

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 45  all /  dec ALICE sensitivity to thermal radiation without and with quenching of the away jet, measured relative to all γ (basically γ from π 0 ) Thermal photons above 3- 4 GeV expected to be measurable Measuring thermal photons

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 46 Summary & Outlook ● First pp run ○ important pp reference data for heavy ions ○ unique physics to ALICE ○ minimum-bias running ○ fragmentation studies ○ baryon-number transport ○ heavy-flavor cross sections Outlook ● High luminosity heavy ion running dedicated high pt electron triggers ○ jets > 100 GeV (EMCAL) ○ Y – states ○  - jet correlations ● pA & light ion running ● First few heavy-ion collisions ○ global event characteristics ○ important bulk properties ● First long heavy-ion run ○ quarkonia measurements ○ Jet-suppression studies ○ flavour dependences

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 47 Some members of the ALICE Collaboration in front of the experiment magnet, 23 July 2008

September 19-21, 2008 Cai Xu: First Physics with ALICE at LHC 中国物理学会 2008 年秋季学术会议：原子核物理与加速器物理 48 Thank you !