JINR Scientific Council 21 January 2005 Participation of

JINR Scientific Council 21 January 2005 Participation of JINR team in the physics of ALICE experiment at LHC (CERN) A. Vodopianov

ALICE Collaboration ~ 1000 Members (63% from CERN MS) ~30 Countries ~80 Institutes

The ALICE Experiment HMPID (RICH) @ high pt TOF PID ( K, p, p ) TRD Electron ID PMD g multiplicity TPC Tracking, d. E/dx ITS Low pt tracking Vertexing PHOS g, 0 MUON m+ m- pairs

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

TRD: Chamber production in Heidelberg, GSI, Dubna, Bucharest Chamber production lab in JINR Chamber production in Heidelberg Electronics and MCM bonding at FZ Karlsruhe

Photon Spectrometer for photons, neutral mesons and -jet tagging • Pb. W 04: Very dense: X 0 < 0. 9 cm Good energy resolution: stochastic 2. 7%/E 1/2 noise 2. 5%/E constant 1. 3% single arm em calorimeter – dense, high granularity crystals; novel material: Pb. W 04; – ~ 18 k channels; ~ 8 m 2; – cooled to -25 o. C; Pb. W 04 crystal

Dimuon Spectrometer • • Study the production of the J/Y, Y', U, U' and U'’ decaying in 2 muons, 2. 4 < < 4 Resolution of 70 Me. V at the J/Y and 100 Me. V at the U RPC Trigger Chambers 5 stations of high granularity pad tracking chambers, over 1200 k channels Complex absorber/small angle shield system to minimize background (90 cm from vertex) Dipole Magnet: bending power 3 T • m

Dipole Magnet assembled and successfully tested, November 2004

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

Study of Quark-Gluon Plasma is the main goal of ALICE experiment

Signatures of quark-gluon plasma § Dilepton enhancement (Shuryak, 1978) § Strangeness enhancement (Muller & Rafelski, 1982) § J/Ψ suppression (Matsui, Satz, 1986) § Pion interferometry (Pratt; Bertsch, 1986) § Elliptic flow (Ollitrault, 1992) § Jet quenching (Gyulassy & Wang, 1992) § Net baryon and charge fluctuations (Jeon & Koch; Asakawa, Heinz & Muller, 2000) § Quark number scaling of hadron elliptic flows (Voloshin 2002) § ……………

Experimental Facilities l AGS ð Beam: ð Users: l SPS ð Beam: ð Users: l RHIC (1986 - 1998) Elab < 15 Ge. V/N, Ös ~ 4 Ge. V/N 400 Experiments: 4 big, several small X 5 (1986 - 2003) Elab < 200 Ge. V/N, Ös < 20 Ge. V/N 600 Experiments: 6 -7 big, several small X 10 (>2000) ð Beam: Ös < 200 Ge. V/N ð Users: 1000 ð Experiments: 2 big, 2 small X 30 l LHC (>2007) ð Beam: Ös < 5500 Ge. V/N ð Users: 1000 ð Experiments: 1 dedicated HI, 3 pp expts

LHC as Ion Collider • Running conditions: Collision system √s. NN (Te. V) L 0 /L 0 (cm-2 s-1) (%) pp 14. 0 5. 5 1034 * 1027 Pb. Pb *Lmax(ALICE) = 1031 70 -50 Run time (s/year) geom. (b) 107 106 ** 0. 07 7. 7 ** Lint(ALICE) ~ 0. 7 nb-1/year • + other collision systems: p. A, lighter ions (Sn, Kr, Ar, O) & energies (pp @ 5. 5 Te. V).

From SPS to RHIC to LHC ‘hotter – bigger – longer lived’ Formation time τ0 3 times shorter than RHIC Lifetime of QGP τQGP factor 3 longer than RHIC Initial energy density ε 0 3 to 10 higher than RHIC SPS RHIC LHC s 1/2(Ge. V) 17 200 5500 d. Nch/dy 500 850 2– 8 x 103 e (Ge. V/fm 3) 2. 5 4– 5 15– 40 Vf(fm 3) 103 7 x 103 2 x 104 QGP (fm/c) <1 1. 5– 4. 0 4– 10 0 (fm/c) ~1 ~0. 5 <0. 2 Central collisions

ALICE Physics Goals ALICE 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

Charmonium (J/ , c , ') production (theory & experiment) The production of J/ and other charmonium states would be suppressed because of: -- dissociation by impact of gluons at the pre-resonance stage. (D. Kharzeev et al. Z. Phys. C 74 (1997) 307. ) -- an absorbtion via the interaction in the hot and dense nuclear matter. (N. Armesto et al. Phys. Rev. C 59(1999) 395; J. Geiss et al. Phys. Lett. B 447 (1999) 31) -- Debye screening of the quark colour charge in the QGP stage, (T. Matsui, H. Satz. Phys. Lett. B 178(1986) or in the pre-QGP stage (mixed phase) via creation of the percolation clusters in the parton percolation model (favorable in last few years) (M. Nardi, H. Zatz. Phys. Lett. B 442(1998)14; S. Digal, S. Fortunato, H. Satz. BI-TP 2003/30. ). .

Parton percolation model: Full QGP stage is reached if the temperature and the density is sufficient, otherwise in the pre-equilibrium stage the local clusters only with QGP inside are created by the percolation mechanizm, i. e. the mixed phase (of partons and hadrons) appears. The expected evolution of nuclear collision. Partonic cluster structure in the transverse collision plane. The Lorentz-contraction makes the nuclei as two thin disks during 0. 1 fm at RHIC. Parton density increases with overlapping of partons and creation of percolation clusters - the condensate of deconfined partons. The percolation condition is np = N r 2/ R 2 1. 128 where N is number of partons with size r ( r is found from the uncertainty relation r 2 /, k. T - partron momentum), R is nuclear radius (R » r)

The cluster size shows the critical behavior, since it increases suddenly near the critical parton density np, i. e. percolation condition starts from some experimental ones : A - number, energy, centrality of the A-A collision. The fractional cluster size and its derivative as function of the parton density n. Charmonium suppression. The tipical time of 0. 2 -0. 3 fm needs formation of the charmonium and also of the parton condensate. If the charmonium is created inside the percolation cluster it can be dissociated by the colour charge screening if rs < rch , where rs and rch are the screening and charmonium radii respectively. The charmonium radii are: r. J/ (0. 9 Ge. V)-1, r (0. 6 Ge. V)-1, r ’ (0. 45 Ge. V)-1. The screening radius is rs = 1/Qs, Qs is screening scale depending from the parton dencity.

Charmonium dissociation as function of centrality. S/Sn The measured J/p suppression as function of centrality from NA-50 experiment at SPS. The screening scale Qs has the critical behaviour from the centrality (Npart is the number of nucleon participants). The charmonium dissociation has two steps in the SPS: for and c at Npart 150 (blue arrow) and for J/ at Npart 250 ( green arrow) No such behaviour is predicted at the RHIC and particulaly at the LHC. S = (J/ )/ (DY) Sn = S for p-A collisions described by the normal absorptions in the nuclear matter (‘normal’ suppression). Two drops of ‘anomalous’ suppression in Pb-Pb are seen at Npart 150 and at Npart 250 in correspondence to the prediction. There is also prediction of strong suppression but the experimental results are still absent.

J/ + - and detection in ALICE 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) Me. V/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 1026 cm-2 s-1. 2. 3 105 J 1800 540 260 Effective mass spectra of ( ) pairs at S/B = 0. 72, at S/B = 7. 1, at S/B = 2. 5, 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 pt > 1. 0 Ge. V/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 5 105 Pb-Pb central events using the TRD for electron identification. J/ S/B = 0. 5 (e+e-) J/ production at 2. 5 < pt < 4 Ge. V/c (e+e-) J/ production from B meson decay (must be taken into account because they are not suppressed)

Light vector mesons production ( , , ) (theory & experiment) -- 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 Ge. V (NA-49, CERN, SPS). .

Light vector mesons production( , , ) (theory & experiment) -- The significant decrease of and masses (by factor up to 150 Me. V/c 2 because partial chiral symmetry restoration in the QGP stage (small effect is for since the isospin structure differs from the one). The effect may be seen in leptonic decay mode (no interactions in the nuclear matter) and only for e+e- in ALICE ( peak is not seen in the level of high combinatorial background since the width is too large). ( M. Asakava, C. M. Ko. Phys, Lett. B 332 (1994) 33) The experimental result shows an evidence of the mass shift for 0 e+e- in Pb-Pb at 160 A Ge. V (NA-45, CERN, SPS). .

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 Ge. V, 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-, K+K- decays the ITS, TPC, TOF and TRD of ALICE will be used for tracking and particle identificatuon. The simulation was done for the ITS, TPC and TOF using the GEANT-3, HIJING model and the last experimental data (the TRD will be included as well). To select the resonance peaks from very high combinatorial background the special cuts were used. Background before the cuts . After the specials cut (S/B = 0. 05) For 5 107 Pb-Pb central events (one month ALICE run)

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. S/B = 0. 06 For 106 Pb-Pb central events. signal after (K+K+) background subtraction with the gaussian fit. The fit results are for the : mass = 1019. 6 0. 04 Me. V/c 2, widht = 4. 43 0. 12 Me. V/c 2

Momentum correlations (HBT) Formalism: Following to Richard Hanbury-Brown and Robert Twiss (HBT) method for an estimation of star sizes JINR physicists G. I. Kopylov & M. I. Podgorecky suggested to study the space - time parameters of sources producing identical particles using the correlation function with Bose. Einstein interferometric effect : 4 vectors: q = p 1 - p 2 , x = x 1 - x 2 (space-time sizes) In practice: CF=1+(-1)S cosq x where S = j 2, j - spin Projections of the momentum difference ql, qo, qs are used to the correspondence axis: l - ‘longitudional’ (beam) direction; o - ‘outward’ direction parallel to transverse pair velocity; S(Qinv) yield of pairs from same event s - ‘sideward’ direction transverse B(Qinv) pairs from “mixed” event to ‘longitudional’ and ‘outward’ N normalization factor, used to normalize the CF to be unity at large,

Momentum correlations (HBT) HBT and the QGP ( - time of emission duration) ·Pratt PRD 1314 (`86): fireball + EOS (Equation of State): ~ 90 fm/c (long emission duration) RHIC correlations results & “HBT Puzzle” • HBT radii decrease with k. T (strong flow) ·Bertsch NPA 173 (89) QGP + cascade: ~ 12 fm/c (long emission duration) • HBT radii increase with increasing centrality (geometrical radius also increases ·Hydro calculation of Rischke &Gyulassy • RO / RS ~ 1 (short emission duration) NPA 608 (1996) 479: Rout/Rside ~ 2 - 4 ·Soff, Bass, Dumitru (PRL 86) • No significant changes in correlation radii AGS SPS RHIC (5 - 6 fm) microscopic transport + hydro with phase transition: Still expect Rout/Rside>1 Transport models and hydro calculations strongly overestimate out and long radii at RHIC. The RHIC data thus points to a new physics: Explosive fireball decay ? AGS: SPS RHIC

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.

Momentum correlations (HBT) 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. 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. Example: Qinv for CF of (π, π). Perfect PID, resolution effects in TPC only, PID by d. E/dx in TPC and impact parameter of the track Example: Qinv for CF of (K+, K-). Perfect PID, resolution effects in TPC only

HBT for direct photons The direct photon interferometry is important for investigation of the very early phase of heavy ion collisions. The following correlation function is considerd: (WA 98, CERN. M. Aggarwal et al. Phys. Rev. Lett. 93 022301(2004)) 1) The radius Rinv = 5. 4 0. 8 fm is near to the one for charged pions. 2)The yield of direct photons was extracted from the equation The results show dominant contribution to the hadronic phase of the direct photon emission. Yield of direct photons versus p. T.

Detection of Upsilons in p-Pb and Pb-p collisions at ALICE muon spectrometer. Analysis of minibias events. bb BGR & Signal Pb-p p-Pb

Analysis ( pt m > 3 Ge. V/c) bb BGR & Signal Pb-p p-Pb

ALICE COMPUTING • 2003 JINR team took responsibility to organize the Physics Data Challenge for all ALICE Institutes situated in Russia; Physics Data Challenge: March - August 2004 -- 107 events processed; LHC Computing GRID (LCG) activity (deployment, test)

Configuration of Ali. En sites in Russia 04 Q 2 – >4 Ali. En operators at work stations SPb. SU JINR PNPI KIAE CERN IHEP server ITEP

Brief analysis of currently available data on Physics Data Challenge (2004) Processed jobs by JINR (2. 0%) Erroneous jobs on JINR site ~ 2500 ~ 404 possible explanation – the RAM capacity of 2 processors batch node (512 MB) is insufficient for processing of two Ali. Root jobs. Large swap. About 10 times more computing power and disk space will be needed for data analysis in 2008!!!

Participation of JINR team in ALICE physics was presented on seminars, workshops and conferences: • 2003: 1. • M. K. Suleimanov, … , A. A. Kuznetsov, A. S. Vodopianov, Analysis of the characteristics of nucleus-nucleus collisions depending on the centrality, Talk presented on VIII International Conference on Nucleus-Nucleus Collisions, 17 -21 June 2003, Moscow, Russia. 2004: 1. 2. 3. 4. A. Vodopianov, Status of the ALICE detector (Invited talk), International Workshop “Quantum Fields and Particles – 3”, Baku, September 2004. B. Batyunya, … , S. Zaporozhets. Simulation of ->K+K- detection in ALICE experiment. Presentation on XVII International Seminar on High Energy Physics Problems, Dubna, 2004. Yu. Kharlov, … , Yu. Bugaenko, V. Korenkov, V. Mitsyn, G. Shabratova et al, Participation nof Russian Sites in the Data Challenge of Alice Experiment in 2004. CHEP-04 “Computing in High Energy and Nuclear Physics” 2004, Interlaken, Switzerland, September 2004. A. Zinchenko, G. Chabratova, V. Pismennaya, A. Vodopianov. Development of Algorithms for Cluster Finding and Track Reconstruction in the Forward Muon Spectrometer of ALICE experiment. CHEP-04 “Computing in High Energy and Nuclear Physics” 2004, Interlaken, Switzerland, September 2004.

Participation of young physicists in ALICE JINR team • Romaina • Russia • Ukraine 2 persons; 3 persons; 1 person;

Joint Workshop on ALICE physics with physicists of Laboratory of Theoretical Physics will take place spring 2005

CONCLUSION • Participation of JINR team in ALICE physics is based on: 1. 2. 3. • • • Contribution to design and construction of particular ALICE subdetectors; Long term participation in the physics and detector simulation; 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. End 2004 four physics groups were named in ALICE (beginning!). 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.