Based on :A.Vodopianov & B.Batyunya

Participation of JINR team in the physics of ALICE experiment

at LHC (CERN)

Program advisory Committee JINR 14-15 April 2005

Heavy Ion program with ALICE (LHC) in JINR Malinina L.V. (JINR, SINP MSU)

The ALICE Experiment

ITSLow pt trackingVertexing

ITSLow pt trackingVertexing

TPCTracking, dE/dxTPCTracking, dE/dx

TRDElectron IDTRDElectron ID

TOFPID ( K, p, )TOFPID ( K, p, )

HMPIDPID (RICH) @ high pt

HMPIDPID (RICH) @ high pt

PHOS, 0 PHOS, 0

MUON pairs MUON pairs

PMD multiplicityPMD 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/ct = 40 fm/c

Heavy Ion Collision

hard collisions pre-equilibrium QGP

hadron gas

freeze-out

ALICE Physics GoalsALICE PPR, 2004, J. Phys. G: Nucl. Part. Phys.

30, 1517-1763

➮ 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 spectrometerin the pseudorapidity interval 2.5 < < 4 and with the mass resolutions about 70 (100) MeV/c2 for J/(). The simulation was carried out for 10% more central Pb-Pb events bythe fast code including acceptance cuts and detector efficiencies andresolutions. The statistics corresponds to the one month running time

at the luminosity of 51026cm-2s-1.

2.3 105 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 decaysof , K, D, B) were included in thesimulation. The trigger cut for muonpt > 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 5105 Pb-Pb central events using the TRD for electron identification.

J/S/B = 0.5

(e+e-)

(e+e-)J/ production at 2.5 < pt < 4 GeV/c

J/

J/ production from B meson decay (must be takeninto 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 /c2 (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 wasfound 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 beexplained 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 ALICEwill 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 3 106 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 pt of (K+K-) pair.

For 106 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 = 1019.6 0.04 MeV/c2, widht = 4.43 0.12 MeV/c2

Interferometry or correlation radii. Momentum correlations(HBT).

P=CF=1+(-1)Scos qxq = p1- p2 , x = x1- x2

momentum correlation measurementsource space-time picture x

Consider a source ofidentical particles whosewave functions can bedescribed as plane waves.

Corresponding normalized probability:

In practice:

total pair spin

S(Qinv) yield of pairs from same event B(Qinv) pairs from “mixed” eventN 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 = {qx , qy , qz} {qout , qside , qlong}, pair velocity v = {vx,0,vz}

Rx2 =½ (x-vxt)2 , Ry

2 =½ (y)2 , Rz2 =½ (z-vzt)2

q0 = qp/p0 qv = qxvx+ qzvz

y side

x out transverse pair velocity vt

z long beam

Podgoretsky SJNP (83) 37; often called BP parameterization

Interferometry radii:

cos qx=1-½ (qx)2… exp(-Rx2qx

2 –Ry2qy

2 -Rz

2qz2

-Rxzqx qz)

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 thatcan be study by ALICE simulation chain usingLednicky’s algorithm.It performs the calculation of the weight of particle pairaccording with quantum statistic and FSI effects.

- + 0 K- K+ K0 p n Λ d t α -

+ 0

K-

K+

K0

p n

Λ d

t α

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: Qinv for CF of (π,π). 2004Perfect PID, resolution effects in TPC only, PID by dE/dx in TPC and impact parameter of the track

Momentum correlations (HBT)

Example: Qinv for CF of (K+,K-).Perfect PID, resolution effects in TPC only

Momentum correlations (HBT)

•HBT radii decrease with kT (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)

•RO / RS ~ 1 (short emission duration)

•Pt 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 0507040, 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 http://cern.ch/lokhtin/hydro, Phys.Lett. B 378 (1996)

5. fast Hydro + UKM

Usually used for HBT simulations among ALICE generators: MeVSim, Hijing, - no space-time information at allSome of the new ones: “simple rescattering model” of T.Humanic (nucl-th 0205053), THERMINATOR (Thermal Heavy Ion Generator, W.Broniovski, W.Florkovski, A.Kisel, T.Taluc nucl-th

0504047)

•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 dataPt-spectra: comparison with PHENIX data

Universal

Hydro

Kinetic

Model

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 2004 -- 107 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.