Based on : A.Vodopianov & B.Batyunya Participation of JINR team in the physics of ALICE experiment at LHC (CERN) Program advisory Committee JINR April 2005 Heavy Ion program with ALICE (LHC) in JINR Malinina L.V. (JINR, SINP MSU)

The ALICE Experiment ITS Low p t tracking Vertexing ITS Low p t tracking Vertexing TPC Tracking, dE/dx TPC Tracking, dE/dx TRD Electron ID TRD Electron ID TOF PID ( K, p, p ) TOF PID ( K, p, p ) HMPID PID high p t HMPID PID high p t PHOS g,  0 PHOS g,  0 MUON m + m - pairs MUON m + m - pairs PMD g multiplicity PMD g multiplicity

JINR participation in ALICE construction Dimuon Spectrometer:  Design of the Dipole Magnet;  Construction and transportation of the Yoke of the Dipole Magnet;  Participation in test beam data analysis;  Physics Simulation; Photon Spectrometer (PHOS):  Delivery of PWO crystals (collaboration w/ Kharkov, Ukraine);  Participation in beam tests at CERN;  Beam test data analysis; Transition Radiation Detector (TRD):  Construction and tests of 100 drift chambers;  Participation in beam tests at CERN;  Physics Simulation;

Dipole Magnet assembled and successfully tested, November 2004

t = - 3 fm/c t = 0 t = 1 fm/c t = 5 fm/c t = 10 fm/c t = 40 fm/c Heavy Ion Collision hard collisions pre-equilibrium QGP hadron gas freeze-out

ALICE Physics Goals ALICE PPR, 2004, J. Phys. G: Nucl. Part. Phys. 30, ➮ Heavy ion observables in ALICE  Particle multiplicities  Particle spectra  Particle correlations  Fluctuations  Jet physics  Direct photons  Dileptons  Heavy-quark and quarkonium production ➮ p-p and p-A physics in ALICE ➮ Physics of ultra-peripheral heavy ion collisions ➮ Contribution of ALICE to cosmic-ray physics

J/    +  - and     detection in ALICE Effective mass spectra of (     ) pairs Muon pairs will be detected in the ALICE forward muon spectrometer in the pseudorapidity interval 2.5 <  < 4 and with the mass resolutions about 70 (100) MeV/c 2 for J/  (  ). The simulation was carried out for 10% more central Pb-Pb events by the fast code including acceptance cuts and detector efficiencies and resolutions. The statistics corresponds to the one month running time at the luminosity of 5  cm -2 s  10 5 J   at S/B = 0.72, 1800   at S/B = 7.1, 540   at S/B = 2.5, 260   at S/B = 1.5. All other muon sources (the decays of , K, D, B) were included in the simulation. The trigger cut for muon p t > 1.0 GeV/c was used.

J/   e + e - detection in ALICE. To study J/  e + e - (at |  | < 1) the TRD and TPC will be used. To find the suppression factor the comparison with a production of open charm particles is supposed (selection of Drell-Yan process is problematical). The preliminary simulation was done for 5  10 5 Pb-Pb central events using the TRD for electron identification. J/  S/B = 0.5 (e+e-) J/  production at 2.5 < p t < 4 GeV/c J/  J/  production from B meson decay (must be taken into account because they are not suppressed)

Light vector mesons production ( , ,  ) -- The enhancement of  yield ( N  /(N  +N  ) ) in central Pb-Pb events as compared to p-p and p-A interactions: up to factor 10 because the supression of Okubo-Zweig-Iizuka rule and a large abundance of strange quarks in the QGP, (A.Shor. Phys.Rev.Lett. 54 (1985) 1122). up to factors 3-4 because the secondary collisions in the nuclear matter (if QGP is not reached). (P.Koch et al. Z.Phys. C 47 (1990) 477). The experimental result is 3.0±0.7 for Pb-Pb at Ebeam=158 A GeV (NA-49, CERN, SPS). -- The decrease of  and  masses by factor up to 150 MeV /c 2 (M.Asakava and S.M.Ko, 1994) because of partial chiral symmetry restoration during the first-order phase transition to the QGP or to the mixed phase (preQGP) according to the conception of A.N.Sysakyan, A.S.Sorin and G.M.Zinoviev. The experiment shows an evidence for the  mass shift at the SPS (NA45).. The predictions are:

Light vector mesons production( , ,  ) (theory & experiment) --The increase of  width by factor 2-3 because of: - Decrease of kaon mass as a consequence of chiral symmetry restoration near the temperature of phase transition to QGP. (D.Lissauer and E.Shuryak. Phys.Lett. B 253 (1991) 15) -- Rescattering of kaons from  decays in the hot and dense nuclear matter. (C.Jonson et al. Phys. Journ. C 18 (2001) 645) The effect may be seen in ALICE by studing of  K + K - decays or by comparison of this decay mode with the  e + e -. There is no experimental evidence for this effect. But 30% difference was found in the slope of pt spectra for  meson obtained from (K + K - ) or (  +  - ) decay modes (in the Pb-Pb at 158 A GeV, CERN SPS). This effect may be explained by the rescattering of kaons in the nuclear matter.

Light vector mesons detection in ALICE. To detect the  e+e- and  e+e- decays the ITS, TPC and TRD of ALICE will be used for tracking and particle identificatuon. The simulation was done for the ITS, TPC and TRD using the GEANT-3, HIJING model and the last experimental data. The particles at p > 1 GeV/c and in the acceptance of all detectors were included to the analysis.   After the specials cut (S/B = 0.2) For 3  10 6 Pb-Pb central events (one month ALICE run)   (Preliminary)

Light vector mesons detction in ALICE. To study the  K + K - decays the ITS, TPC and TOF were applied for the simulation To select the resonance peaks from the combinatorial background the cuts were used for p t of (K + K - ) pair. For 10 6 Pb-Pb central events. S/B = 0.06  signal after (K+K+) background subtraction with the gaussian fit. The fit results are for the  : mass =  0.04 MeV/c 2, widht = 4.43  0.12 MeV/c 2

Interferometry or correlation radii. Momentum correlations(HBT). P=CF=1+(-1) S  cos q  x  q = p 1 - p 2,  x = x 1 - x 2 momentum correlation measurement  source space-time picture  x  Consider a source of identical particles whose wave functions can be described as plane waves. Corresponding normalized probability: In practice : total pair spin S(Qinv) yield of pairs from same event B(Qinv) pairs from “mixed” event N normalization factor, used to normalize the CF to be unity at large Qinv

“General” parameterization at |q|  0 Particles on mass shell & azimuthal symmetry  5 variables: q = {q x, q y, q z }  {q out, q side, q long }, pair velocity v = {v x,0,v z } R x 2 =½  (  x-v x  t) 2 , R y 2 =½  (  y) 2 , R z 2 =½  (  z-v z  t) 2  q 0 = qp/p 0  qv = q x v x + q z v z y  side x  out  transverse pair velocity v t z  long  beam Podgoretsky SJNP (83) 37; often called BP parameterization Interferometry radii:  cos q  x  =1-½  (q  x) 2  …  exp(-R x 2 q x 2 –R y 2 q y 2 -R z 2 q z 2 -R xz q x q z ) RL (78) This picture is borrowed from R. Lednicky talk at Warsaw meeting, 2003

The chain for the simulation of particle correlations in ALICE

Momentum correlations (HBT) Simulations of particle correlations in ALICE. The different particles systems that can be study by ALICE simulation chain using Lednicky’s algorithm. It performs the calculation of the weight of particle pair according with quantum statistic and FSI effects.

Influence of particles identification and resolutions effects in ALICE detectors: TPC, ITS, TOF on correlation functions was studied using HIJING model and Lednitsky’s algorithm for calculation of particle correlations. To study particle correlations the ITS, TPC, TOF and TRD of ALICE will be used for tracking and particle identification. The simulation was done for the ITS, TPC and TOF using the GEANT code. Example: Q inv for CF of (π,π) Perfect PID, resolution effects in TPC only, PID by dE/dx in TPC and impact parameter of the track Momentum correlations (HBT) Example: Q inv for CF of (K+,K-). Perfect PID, resolution effects in TPC only

Momentum correlations (HBT) HBT radii decrease with k T (strong flow) HBT radii increase with increasing centrality (geometrical radius also increases unexpected small sizes: no significant changes in correlation radii AGS  SPS  RHIC (5 - 6 fm) R O / R S ~ 1 (short emission duration) P t dependence do not agree with hydro RHIC correlations results & “HBT Puzzle” For ALICE HBT simulations we need of Monte Carlo generator which: -- includes resonances decays; -- includes flow; -- takes into account hadronic rescatterings, -- jets; -- is rapid; -- is flexible; Realization: 1. UKM modification under ROOT framework 2. UKM test: N.S. Amelin, R. Lednicky, T.A. Pocheptsov, L.V. Malinina, Yu. Sinyukov nucl-th , submitted to Phys. Rev. C 3. Statistical approach, particle ratios 4. Fast hydro code creation and comparison with RHIC data. -- Hubble -- MSU I.P. Lokhtin and A.M. Snegirev Phys.Lett. B 378 (1996) 5. fast Hydro + UKM Usually used for HBT simulations among ALICE generators: MeVSim, Hijing, - no space-time information at all Some of the new ones : “simple rescattering model” of T.Humanic (nucl-th ), THERMINATOR (Thermal Heavy Ion Generator, W.Broniovski, W.Florkovski, A.Kisel, T.Taluc nucl-th ) Success of “blast wave” parameterisation Success of T. Humanic rescattering model Necessity of proper treatment of resonances Necessity of NonGaussian shape analysis

Artificial resonance source (π+π+) Qinv CF : The resonances contributions in pion spectra. Momentum correlations (HBT) η’ 1000 fm/c. mean life time τ = 1.3 fm/c 23.4 fm/c. CF(kt): comparison with STAR data Pt-spectra: comparison with PHENIX data U niversal H ydro K inetic M odel

ALICE COMPUTING 2003 JINR team took responsibility to organize the Physics Data Challenge for all ALICE Institutes situated in Russia; Physics Data Challenge in all collaboration: March - August events processed; (2% in JINR site now, but computing power has to be increased by about 10 times ) LHC Computing GRID (LCG) activity (deployment, test)

CONCLUSIONS Participation of JINR team in ALICE physics is based on: 1.Contribution to design and construction of particular ALICE sub- detectors; 2.Long term participation in the physics and detector simulation; 3.Practical knowledge and experience in using of distributed computing (GRIID & LCG) for data analysis. Achievements of JINR team are recognized by ALICE. JINR team has leading positions in some physics tasks. At the end of 2004 four physics groups were named in ALICE. Convener of one of these groups is JINR physicist Y. Belikov. JINR team presents scientific results on workshops & conferences. It is planned that the most of the data analysis carried by JINR, will be done at Dubna. Computing power has to be increased by about 10 times.