Prospects for First Measurements with ALICE in Pb+Pb Collisions at the LHC LHC. Alice. Dedicated general purpose Heavy Ion experiment at LHC

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1 Prospects for First Measurements with ALICE in Pb+Pb Collisions at the LHC LHC Alice Dedicated general purpose Heavy Ion experiment at LHC

2 Heavy Ions at the LHC Determine Initial Conditions What is the extent of shadowing, saturation, CGC? sets the stage for particle production / dynamics Expect different timescales, shorter interaction times, higher energy (T) compared to RHIC! Does system still equilibrate rapidly? Thermal model still apply? T still ~ T c (lattice QCD)? Does it flow? Elliptic Flow change? v 2 still saturated? More or less v 2? p T dependence? Is the QGP still strongly- (or weakly-) coupled? Liquid? More like a gas? No longer nearly-perfect fluid flow? viscosity? Impact on energy loss!! Understand parton energy loss! What are the microscopic processes? mass and flavor dependence? use high p T jets & tag heavy quark jets Understand response of the medium! Strongly interacting quarks and gluons away-side response? use punch-through & associated jet Color screening of the medium! Deconfinement? (compare LQCD), initial T, other effects J/ψ & Y states

ALICE Collaboration ~ 1000 Members (63% - CERN States) ~ 30 Countries ~ 100 Institutes US ALICE 13 Institutions 57 members (inc. 12+ grad. students) Cal. St. U. San Luis Obispo, Chicago St.

3 ALICE Collaboration ~ 1000 Members (63% - CERN States) ~ 30 Countries ~ 100 Institutes US ALICE 13 Institutions 57 members (inc. 12+ grad. students) Cal. St. U. San Luis Obispo, Chicago St. University, Creighton University, University of Houston, Lawrence Berkeley Nat. Lab, Lawrence Livermore Nat. Lab, Oak Ridge Nat. Lab, Ohio State University, Purdue University, University of Tennessee, University of Texas at Austin, Wayne State University, Yale University India Armenia Ukraine Mexico JINR Russia Romania Spain/Cuba Japan South Africa USA China Croatia Netherlands Hungary UK Greece Sweden Poland Norway Slovak Rep. Czech Rep. Brazil Korea CERN Denmark Italy France Germany Finland

4 The ALICE Experiment Fully Installed & Commissioned Hadron & µ Capabilities ITS, TPC, TOF, HMPID, MUONS, V0, T0, ZDC, ACORDE, TRIGGER, DAQ, HLT, DCS

5 The ALICE Experiment EM (e and γ ) Partial Capabilities - (now, after next installation in % below) TRD (40, 100%), PHOS (60, 80%) & EMCAL (40, 160 (inc. DCal) %) complete John Harris (Yale U.) US LHC User s Meeting, 24 October 2008

Soft Physics in ALICE at the LHC LHC Heavy Ions in general expectations based on pqcd predictions & RHIC results a lesson from RHIC guided by theory + versatility + expect

6 Soft Physics in ALICE at the LHC LHC Heavy Ions in general expectations based on pqcd predictions & RHIC results a lesson from RHIC guided by theory + versatility + expect the unexpected Soft Physics (p T 2 GeV/c) with heavy ions at LHC Smooth extrapolation from SPS RHIC LHC? ALICE to measure comprehensive set of observables to determine dynamics

7 ALICE Detectors & Acceptance central barrel -0.9 < η < 0.9 φ = 2π tracking, PID (TPC/ITS/ToF) single arm RICH (HMPID) single arm e.m. cal (PHOS) electron id (TRD) EM calorimeter arms (EMCal + DCal) (charged particles) forward muon arm -4 < η < -2.4 absorber, 3 T-m dipole magnet 10 tracking + 4 trigger chambers µ arm multiplicity detectors -5.4 < η < 3 including photon counting in PMD trigger & timing detectors 6 Zero Degree Calorimeters T0: ring of quartz window PMT's V0: ring of scint. Paddles

Material Budget Cumulative mid-rapidity material budget

CMS x/x0 (%) Beam pipe 0.26 Beam pipe 0.45 Beam pipe 0.

2 cm) 7.23 ITS (50 cm) 7.43 SCT (52 cm) 14.

8 Material Budget Cumulative mid-rapidity material budget for ALICE, ATLAS and CMS ALICE x/x0 (%) ATLAS x/x0 (%) CMS x/x0 (%) Beam pipe 0.26 Beam pipe 0.45 Beam pipe 0.23 Pixels (7.6 cm) 2.73 Pixels (12 cm) 4.45 Pixels (10.2 cm) 7.23 ITS (50 cm) 7.43 SCT (52 cm) TIB (50 cm) TPC (2.6 m) 13 TRT (1.07 m) TOB (1.1 m) Reconstruction and identification possible at low p T due to low material budget B.Hippolyte Hot Quarks Estes Park

9 ALICE Tracking Efficiencies, Momentum Resolutions Detector performance published in J. Phys.G32 (2006) 1295 Detector tracking efficiencies Detector momentum resolutions Central PbPb Cosmic ray data

10 Energy Loss (de/dx) and PID in TPC de/dx as shown by Federico < 6 % resolution measured in p + p separation power Expect ~6.5% resolution in central Pb+Pb to 50 GeV 5/25/2010

11 Identified Particle Spectra Particle reconstruction and identification capabilities: a strength of ALICE Global tracking (ITS-TPC-TRD) & de/dx (low p T + relativ. rise), TOF, HMPID, PHOS, EMCal Also invariant mass & topological reconstruction Acceptance / efficiency / reconstruction (ε) / contamination p T range (PID or stat. limits) for 10 7 central PbPb and 10 9 min. bias pp For ~ 20 particle species for -1 < y < +1 and -4 < y < +2.5 π, K, p: to 50 GeV Weakly/strongly decaying particles/resonances to GeV Mid-rapidity Pb-Pb π K p PID in the relativistic rise Pb-Pb + EMCal p T (GeV/c)

N spec N part Impact parameter (b) LHC PbPb design: L = 5 x 10 26 cm -2 s -1

12 Centrality Determination in ALICE and 2010 Rates Event by event determination of centrality: Zero Degree Calorimeters (ZDC = ZP + ZN) + Z EM cal s (ZEM) E(ZDC), E(ZEM) N spec N part Impact parameter (b) LHC PbPb design: L = 5 x cm -2 s -1 Possibilities for 2010 PbPb Run: L ~ cm -2 s -1, ~ 100 Hz, t ~10 6 s Ldt ~ 0.01 nb -1 ~ 10 8 events

13 Soft Physics in ALICE Event Characterization (baseline, shadowing, CGC,. ) Multiplicity, centrality, transverse momentum and pseudo-rapidity distributions

14 Initial Conditions at the LHC N. Armesto, arxiv: LHC predictions: An overview LHC (dn/dy) (2600) Establish initial conditions at LHC Measure particle multiplicities shadowing, gluon saturation, CGC? establish the topology for particle production and dynamics at LHC! Particle Multiplicities (1200)

15 Soft Physics in ALICE at the LHC Measure spectra & yields (vs centrality/multiplicity) with heavy ions Transverse Momentum (p T ) Distributions Tracking in TPC + ITS p T versus Multiplicity Preliminary <p t > in 0.3 to 4 GeV TPC p t spectrum Preliminary <p t > versus multiplicity to tune Monte Carlo programs (and watch for surprises?)

16 Soft Physics in ALICE Event Characterization (baseline, shadowing, CGC,. ) Multiplicity, centrality, transverse momentum and pseudo-rapidity distributions Bulk Properties of the Medium (T, µ, ) Particle ratios, hadronic resonances

17 Soft Physics ALICE Performance Weak decay vertex reconstruction of strange particles K 0 s ππ Λ πp PDG: MeV PDG: MeV p T reach (with 10 7 events): GeV/c (φ, K, Λ) 8-12 GeV/c (ρ, Ξ, Ω)

18 Soft Physics in ALICE at the LHC Measure particle spectra and yields with heavy ions at LHC identified mesons, baryons and resonances including flavor production (strangeness, charm and beauty) Chemical freezeout temperature ~175 MeV? If not, we are completely wrong about interpretation of RHIC data! Twice initial T, still freezes out at T cr? Had better! T, µ B and volume are only parameters connected to QCD phase boundary B. Hippolyte et al. (ALICE) Eur. Phys. J. C49 (2007) 121. Equ. Non-Equ.

19 Soft Physics in ALICE Event Characterization (baseline, shadowing, CGC,. ) Multiplicity, centrality, transverse momentum and pseudo-rapidity distributions Bulk Properties of the Medium (T, µ, ) Particle ratios, hadronic resonances Chiral Symmetry Restoration? Short-lived resonances & medium-modified masses Collision Dynamics (space-time evolution, transport properties) Momentum correlations (HBT) Collective Flow (radial, anisotropic) Baryon number transport Fluctuations Event-by-event particles, momentum,

20 Resonances (ρ, φ, K*, ) Hadrons Short-lived resonances: Time difference between chemical and kinetic freeze-out In medium modifications of mass, width, comparison of hadronic and leptonic channels partial chiral symmetry restoration? Reconstruct invariant mass spectrum, subtract background (like-sign method). Mass resolutions ~ MeV. p T statistical limits: 8 (ρ) to 15 GeV/c (φ,k*) ρ 0 (770) π + π 10 6 central Pb-Pb Mass resolution ~ 1.2 MeV φ (1020) K + K - K*(892) 0 K π central Pb-Pb Mass resolution ~ 2-3 MeV Invariant mass (GeV/c 2 ) Invariant mass (GeV/c 2 ) Invariant mass (GeV/c 2 )

21 Resonances (φ, ω, J/ψ) e + e - Short-lived resonances: In medium modifications of mass, width? Compare hadronic & leptonic channels partial chiral symmetry restoration? 2 x 10 7 Pb+Pb events φ φ ω, φ: S/B ~ J/ψ: S/B ω J/ψ

22 Short-lived resonances: Resonances (φ, ω, J/ψ) e + e - In medium modifications of mass, width? Compare hadronic & leptonic channels partial chiral symmetry restoration? 2 x 10 7 Pb+Pb events

23 Short-lived resonances: Resonances (φ, ω, J/ψ) e + e - In medium modifications of mass, width? Compare hadronic & leptonic channels partial chiral symmetry restoration? 2 x 10 7 Pb+Pb events 2 x 10 7 Pb+Pb events - ω, φ: significance = J/ψ: significance = 40-50

24 Soft Physics in ALICE Event Characterization (baseline, shadowing, CGC,. ) Multiplicity, centrality, transverse momentum and pseudo-rapidity distributions Bulk Properties of the Medium (T, µ, ) Particle ratios, hadronic resonances Chiral Symmetry Restoration Short-lived resonances & medium-modified masses Collision Dynamics (space-time evolution, transport properties) Momentum correlations (3D HBT one of first measurements) Collective Flow (radial, anisotropic) Baryon number transport Fluctuations Event-by-event particles, momentum,

v 2 Predictions for the LHC Heinz, Kolb, Sollfrank Hirano, to check reference. Hirano et al, nuclth/0701075v2 N.Borghini and U.A.Weidemann, J.Phy.

25 v 2 Predictions for the LHC Heinz, Kolb, Sollfrank Hirano, to check reference. Hirano et al, nuclth/ v2 N.Borghini and U.A.Weidemann, J.Phy.G 35 (2008) v 2 by ALICE in 1 st Pb + Pb Run Identified particle v 2 as a function of centrality to at least p T = 10 GeV/c resonances, strangeness including charm!

26 Significant increase at LHC Abundance of heavy flavors probe early times, calculable Heavy Flavor in ALICE σ Rate σ cc (LHC) ~ 10 σ cc (RHIC) σ bb (LHC ) ~ 100 σ bb (RHIC) Open Charm & Beauty (mass/color charge dep. of parton E-loss) Displaced vertices (D o K - π+, B e + hadrons) from TPC/ITS, TRD/EMCal Electrons in Transition Radiation Detector (TRD)

27 K Open Charm and Beauty TOF (K/π id) TPC (tracking) π ITS (vertexing) under study D 0 Kπ D + Kππ D s KKπ D* D 0 π D 0 Kπρ Λ c πkp DIS London Andrea Dainese 27 Courtesy A. Dainese

28 e Open Charm and Beauty TPC (tracking) ITS (vertexing) ITS (vertexing) TPC (tracking e/π id) TRD & EMCal (e/π id) under study under study D 0 Kπ D + Kππ D s KKπ D* D 0 π D 0 Kπρ Λ c πkp B e+x B 5 pr. B J/ψ ee DIS London Andrea Dainese 28 Courtesy A. Dainese

29 Open Charm and Beauty µ under study MUON (tracking,id) under study D 0 Kπ D + Kππ D s KKπ D* D 0 π D 0 Kπρ Λ c πkp B e+x B 5 pr. B J/ψ ee B µ+x DIS London Andrea Dainese 29 Courtesy A. Dainese

Primary resolution from 2 layers of silicon pixel detector

30 Displaced Vertices: Track DCA* Resolution * Distance of Closest Approach (impact parameter with primary vertex) Primary resolution from 2 layers of silicon pixel detector rec. track e Primary Vertex dca B X Two layers: r = 4 cm r = 7 cm

31 Charm & Beauty in ALICE R AA D 0 Kπ D + Kππ B e + X m C = 1.2 GeV m C = 0 Calculations: Armesto, Dainese, Salgado, Wiedemann B e 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events)) m b = 4.8 GeV

32 Heavy Quarks in ALICE - p t Coverage D 0 Kπ B e + X electron 1 year at nominal luminosity (10 7 central Pb-Pb events, 10 9 pp events)

33 Expectations in 2010 for Heavy Quarks at LHC D 0 Kπ 7 TeV p + p and 2.75 TeV Pb + Pb pp Mangano, Nason, Ridolfi, NPB373 (1992) 295. Gluon shadowing MNR with CTEQ6M + shadowing [mean of EKS98/EPS08] for Pb system : s NN : QQ NN QQ σ NN [mb] QQ N tot QQ N tot EKS 98 shadowing EKS 98 C shadowing [mb] Pb-Pb (0-5%) Pb-Pb (0-5%) pp pp 5.5 TeV 2.75 TeV 14 TeV 7 TeV Charm/beauty Charm/beauty Charm/beauty Charm/beauty 3.4 / / / / / / / / / /

34 2010 PbPb in ALICE D 0 p t Coverage Nominal LHC year 2.75 TeV PbPb 1 st year D 0 Kπ 14 TeV 10 9 min. bias evts 5.5 TeV % central evts For lower s NN = 2.75 TeV Scale signal with cross section reduction Bkg change from dn ch /dy=6000 (PPR) to 2000 (more realistic) Charm p T spectrum to 15 GeV/c in 1 st run

35 Quarkonia in ALICE Measured in both the di-electron (midrapidity, TRD, EMCal) and di-muon (forward rapidity, MUON) channels e e ITS (vertexing) TPC (tracking) TRD & EMCal (e/π id) µ µ MUON (tracking,id) Courtesy A. Dainese 35

Muon detection The ALICE Muon Arm Acceptance: φ = 2π 4.0 < η < 2.5 (θ = 2 9 ) Absorber for hadrons and photons 10 planes of high granularity tracking Dipole Magnet (0.

36 Muon detection The ALICE Muon Arm Acceptance: φ = 2π 4.0 < η < 2.5 (θ = 2 9 ) Absorber for hadrons and photons 10 planes of high granularity tracking Dipole Magnet (0.7 T, 3 Tm) Muon filter (4 GeV/c threshold for µ) 4 planes of trigger chambers Muon detection in Pb + Pb Expect few hundred particles in muon chambers Maximum hit density expected ~ 0.05 cm 2 Cathode pad chambers for tracking with variable segmentation Resistive-plate chambers for trigger

Ultimate ALICE Quarkonia Performance dn ch /dy = 4000 in central Pb-Pb Particle Charmonia µ + µ - Charmonia e + e - Bottomonia Bottomonia µ + µ - e + e - Bkg-sub mass plot acc. η -4 < η < -2.5 η < 0.

37 Ultimate ALICE Quarkonia Performance dn ch /dy = 4000 in central Pb-Pb Particle Charmonia µ + µ - Charmonia e + e - Bottomonia Bottomonia µ + µ - e + e - Bkg-sub mass plot acc. η -4 < η < -2.5 η < < η < -2.5 η < 0.9 M res. 65 MeV 35 MeV 90 MeV 90 MeV S / (S+B) (1 mo.) J/ψ 150, ψ 7 J/ψ 245 5/25/2010 ϒ 30, ϒ 12, ϒ 8 ϒ 21, ϒ 8 ψ, ψ ψ, ψ ϒ, ϒ,ϒ ϒ, ϒ, no ϒ p t J/ψ 0-20 GeV J/ψ 0-10 GeV ϒ 0-8 GeV --

38 2010 Pb + Pb Quarkonia in ALICE Most Optimistic Scenario (0.05 nb -1 ) J/ψ in 5 centrality bins Centrality bin Signal (10 3 counts) Background (10 3 counts) Signal Background S S+B J/ψ p T dependence up to 20 GeV/c measured in each bin J/ψ polarization ψ to J/ψ ratio, maybe vs centrality (tbd) Ψ p T dependence (no centrality dependence) Ψ and Ψ yields and ratios in at most 3 centrality bins Realistic pessimistic: J/ψ vs centrality, no ψ ; Ψ and Ψ ratios

39 High p T Particles and Jets in ALICE

40 High p T Particles and Jet Rates in ALICE ALICE hard probe physics capabilities: - Electron/hadron disc. (TRD, EMCal) - µ measurements (forward muon arm) - Good γ/π 0 discrimination (EMCal, PHOS) - Fast trigger on jets (EMCal) Hard Probe statistics in ALICE: 0.5 nb /year in nominal minbias Pb+Pb run inclusive jets: E T ~ 200 GeV dijets: E T ~ 170 GeV π 0 : p T ~ 75 GeV inclusive γ: p T ~ 45 GeV PHOS x 6 lower TPC x 3 higher inclusive e: p T ~ 30 GeV Thanks Peter Jacobs

41 Neutral Pion Reconstruction Conversion electrons measured in TPC PHOS and EMCal 7 TeV p + p PHOS PHOS π 0 η Mixed event background EMCal EMCal

(p+p) = 10, 100, 300 nb -1 L dt (pp) = 10 nb -1 ~ same # binary collisions in L

42 Simulated Neutral Pion Spectra in PHOS π 0 η π 0 spectra to p T ~ 30,40,50 GeV/c for L dt (p+p) = 10, 100, 300 nb -1 η spectra to p T ~ 20,35,45 GeV/c for L dt (p+p) = 10, 100, 300 nb -1 L dt (pp) = 10 nb -1 ~ same # binary collisions in L dt (PbPb) = 0.01 nb -1! π 0 spectra to p T ~ 30 GeV/c, η spectra to p T ~ 20 GeV/c

43 Di-hadron Correlations in ALICE Expectation for 1 st PbPb Run: trigger hadron bins to > 30 GeV/c select ensembles of trigger/associated PID study centrality dependence determine origin!

44 What About the Ridge at LHC Is the ridge present at LHC? If so, investigate dependence on: p trig T and p assoc T centrality particle type

.] Parton energy loss in High T QCD medium Requires detailed measurements for theoretical comparison / understanding Establish energy-loss

45 Jets in Heavy Ion Collisions at RHIC & LHC Central Au+Au s NN =200 GeV EMC + tracking data E T jet ~ 21 GeV Central Pb+Pb s NN =5.5 TeV EMCal + tracking sim. E jet T ~ 120 GeV Why measure jets in heavy ion collisions? [inclusive, di-jets, hadron-jet, γ-jet,..] Parton energy loss in High T QCD medium Requires detailed measurements for theoretical comparison / understanding Establish energy-loss mechanisms energy flow within jets, quark vs gluon jet differences Flavor and mass dependence, fragmentation modification Medium response to parton energy loss establish properties of the medium

46 Considerations for Jet Reconstruction in ALICE Jet reconstruction works for tracking + EM calorimetry (from RHIC experience) Detector resolution sufficient Systematic uncertainties understood Many Biases (affecting jets) take into account: Trigger Effects (online & offline) Event backgrounds (on average and fluctuations) Algorithms (esp. seeded, effects on HI jet results, treatment of HI background) p T cuts on tracking and calorimetry Simulations approach in ALICE (with EMCal) Utilize anti-kt (less background sensitivity) for jet reconstruction Full GEANT for detector response PYTHIA, qpythia (available quenching model) for jets HIJING (central Pb+Pb at 5.5 TeV) for background Bottom-line Consider all effects simulate/estimate systematic uncertainties Reduce/eliminate p T cuts, assess background & fluctuations Background effects require delicate unfolding procedure (doable)

Jet Reconstruction in Heavy Ion Collisions Primary Jet

algorithms Cone shape restriction Seeded-cone & strong

Recombination algorithms kt (anti-kt) starts from low (high)

disfavored Recombination algorithms K T jet anti-kt jet R

47 Jet Reconstruction in Heavy Ion Collisions Primary Jet Reconstruction Approaches Cone algorithms Cone-based algorithms Cone shape restriction Seeded-cone & strong trigger seed biases jet Hard scattering Fragmentation Recombination algorithms kt (anti-kt) starts from low (high) p T merges weighted by 1/ p T (p T ) high (low) p T disfavored Recombination algorithms K T jet anti-kt jet R resolution parameter In Jet Reconstruction in ALICE utilize anti-kt (less background sensitivity)

48 Underlying Event Background B ia (A i ) = E i ρ A i ALICE EMCal Physics Performance Report (Nov. 2009):

49 Inclusive Jets Systematic Uncertainties* (*with EMCal) ALICE EMCal Physics Performance Report (Nov. 2009):

50 ALICE Inclusive Jet Cross Section Measurement Capabilities with EMCal

51 Jets in ALICE with EMCal: R AA Central Pb+Pb s NN =5.5 TeV Jet systematic uncertainties small! Measurements possible to 200 GeV statistically and systematically

5 TeV qpythia not optimized (yet) do not draw conclusions from shape diff s.

52 Jet Broadening at RHIC & ALICE with EMCal Ratio of jet yields within R = 0.2 vs R = 0.4 using anti-kt algorithm Central Au+Au s NN =200 GeV Central Pb+Pb s NN =5.5 TeV qpythia not optimized (yet) do not draw conclusions from shape diff s. Jet energy profile (AuAu data) BROADENED indicating JET QUENCHING! Small experimental systematic uncertainties in measurements (ratios from same exp. and data set) a precision measurement in ALICE!

53 ALICE EMCal Jet Trigger

54 Charged Jets in TPC in ALICE in 2010 Central Pb+Pb s NN =5.5 TeV Charged jets 1/3 of jet energy First Year Charged Jets Eventually Charged + EMCal R < 0.4 central Pb+Pb Statistics for 1 month of Pb+Pb running (10 3 jets at 100 GeV in 10 6 Pb+Pb interactions)

55 ALICE Prospects for First Physics First physics in ALICE is NOW pp important reference data for heavy-ions Examples: multiplicity distribution, baryon transport identified particle spectra measurement of charm cross section major input to pp QCD physics First 10 5 PbPb events: global event properties multiplicity, rapidity density, charged particle spectra elliptic flow First 10 6 PbPb events: source characteristics and spacetime evolution identified particle spectra, resonances differential flow analysis particle correlations, interferometry First 10 7 PbPb events: high-p T and heavy flavors suppression, jet quenching, heavy flavor energy loss charmonium production Eventual goals - bulk properties of medium & parton energy loss mechanisms energy density, temperature, pressure heat capacity/entropy, viscosity, sound velocity, opacity susceptibilities, order of phase transition

ALICE at LHC Overview & Jet Physics LHC

ALICE at LHC Overview & Jet Physics Alice LHC Dedicated general purpose Heavy Ion experiment at LHC ALICE Collaboration ~ 1000 Members (63% - CERN States) ~ 30 Countries ~ 100 Institutes ~ 150 M CHF capital