Participation of JINR team in the physics of ALICE

experiment at LHC (CERN)

A.Vodopianov

JINR Scientific Council

21 January 2005

ALICE Collaboration

UKPORTUGAL

JINR

GERMANY

SWEDENCZECH REP.

HUNGARYNORWAY

SLOVAKIAPOLANDNETHERLANDS

GREECE

DENMARKFINLAND

SWITZERLAND

RUSSIA CERN

FRANCE

MEXICOCROATIA ROMANIA

CHINA

USAARMENIA

UKRAINE

INDIA

ITALYS. KOREA

~ 1000 Members

(63% from CERN MS)

~30 Countries

~80 Institutes

0

200

400

600

800

1000

1200

1990 1992 1994 1996 1998 2000 2002 2004

ALICE Collaboration statistics

LoI

MoU

TP

TRD

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 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; Preparation for beam tests at BNL;

• Transition Radiation Detector (TRD): 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

Electronics and MCM bonding at FZ Karlsruhe

Chamber production in Heidelberg

for photons, neutral mesons and -jet tagging

PbW04: Very dense: X0 < 0.9 cmGood energy resolution:stochastic 2.7%/E1/2

noise 2.5%/Econstant 1.3%

Photon Spectrometer

PbW04 crystal

• single arm em calorimeter– dense, high granularity

crystals; novel material: PbW04;

– ~ 18 k channels; ~ 8m2;– cooled to -25oC;

Dimuon Spectrometer• Study the production of the J/, ', , ' and

'’ decaying in 2 muons, 2.4 < < 4• Resolution of 70 MeV at the J/ and 100 MeV

at the

Dipole Magnet: bending power 3 T•m

Complex absorber/small angle shield system to minimize background(90 cm from vertex)

RPC Trigger Chambers

5 stations of high granularity pad tracking chambers, over 1200k channels

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

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 AGS (1986 - 1998) Beam: Elab < 15 GeV/N, s ~ 4 GeV/N Users: 400 Experiments: 4 big, several small

SPS (1986 - 2003) Beam: Elab < 200 GeV/N, s < 20 GeV/N Users: 600 Experiments: 6-7 big, several small

RHIC (>2000) Beam: s < 200 GeV/N Users: 1000 Experiments: 2 big, 2 small

LHC (>2007) Beam: s < 5500 GeV/N Users: 1000 Experiments: 1 dedicated HI, 3 pp expts

X 5

X 10

X 30

LHC as Ion Collider• Running conditions:

• + other collision systems: pA, lighter ions (Sn, Kr, Ar, O) & energies (pp @ 5.5 TeV).

Collision system

PbPb

pp

<L>/L0

(%)

107

Run time

(s/year)

geom.

(b)

L0

(cm-2s-1)

√sNN

(TeV)

0.071034 * 14.0

70-50 106 ** 7.710275.5

*Lmax(ALICE) = 1031 ** Lint(ALICE) ~ 0.7 nb-1/year

From SPS to RHIC to LHC‘hotter – bigger – longer lived’

<0.2~0.5~10 (fm/c)

4–101.5–4.0<1QGP (fm/c)

2x1047x103103Vf(fm3)

15–404–52.5 (GeV/fm3)

2–8x103850500dNch/dy

550020017s1/2(GeV)

LHCRHICSPSCentral collisions

Formation time τ0 3 times shorter than RHICLifetime of QGP τQGP factor 3 longer than RHICInitial energy density ε0 3 to 10 higher than RHIC

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

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. B178(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:

The expected evolution of nuclear collision.

Partonic cluster structure in the

transverse collision plane.

Full QGP stage is reached if the temperatureand 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 Lorentz-contraction makes the nucleias two thin disks during 0.1 fm at RHIC. Parton density increases with overlapping of partons and creation of percolationclusters - the condensate of deconfined partons. The percolation condition is np = Nr2/R2 1.128 where N is number of partons with size r ( r is found from the uncertainty relation r2 /<k2

T>, kT - partron momentum), R is nuclear radius (R » r)

The fractional cluster size and its derivativeas function of the parton density n.

The cluster size shows the criticalbehavior, since it increases suddenlynear the critical parton density np, i.e.percolation condition starts from someexperimental ones : A - number, energy,centrality of the A-A collision.

Charmonium suppression.The tipical time of 0.2 -0.3 fm needs for 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: rJ/ (0.9 GeV)-1, r (0.6GeV)-1, r’ (0.45 GeV)-1. The screening radius is rs = 1/Qs, Qs is screening scale depending from the parton dencity.

Charmonium dissociation as function ofcentrality.

The measured J/p suppression asfunction of centrality from NA-50experiment at SPS.

S/Sn

The screening scale Qs has the critical behaviour from the centrality(Npart is the number of nucleon -participants). The charmoniumdissociation 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 bythe normal absorptions in the nuclearmatter (‘normal’ suppression).

Two drops of ‘anomalous’ suppressionin Pb-Pb are seen at Npart 150 and atNpart 250 in correspondence to theprediction. There is also prediction of strong suppression but the experimental resultsare still absent.

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 (, , )

(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 GeV (NA-49, CERN, SPS).

.

Light vector mesons production(, , ) (theory &

experiment) -- The significant decrease of and masses (by factor up to 150 MeV/c2 ) 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

0e+e- in Pb-Pb at 160 A GeV (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 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-, e+e-, K+K- decays the ITS, TPC, TOFand 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.

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

Momentum correlations (HBT)Formalism:

CF=1+(-1)Scosqxwhere S = j2, j - spin

4vectors: q = p1- p2 , x = x1- x2

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,

l - ‘longitudional’ (beam) direction;o - ‘outward’ direction parallel to transverse pair velocity; s - ‘sideward’ direction transverse to ‘longitudional’ and ‘outward’

In practice:Projections of the momentum difference ql, qo, qs are usedto the correspondence axis:

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 :

21021 , ttxxxx

(space-time sizes)

2qQinv

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 ?

Momentum correlations (HBT)

•HBT radii decrease with kT (strong flow)

•HBT radii increase with increasing centrality (geometrical radius also increases

•RO / RS ~ 1 (short emission duration)

•No significant changes in correlation radii AGS SPS RHIC (5 - 6 fm)

RHIC correlations results & “HBT Puzzle”

HBT and the QGP

·Pratt PRD 1314 (`86): fireball + EOS

(Equation of State): ~ 90 fm/c (long emission duration)

·Bertsch NPA 173 (89) QGP + cascade:

~ 12 fm/c (long emission duration)

·Hydro calculation of Rischke &Gyulassy

NPA 608 (1996) 479: Rout/Rside ~ 2 - 4

·Soff, Bass, Dumitru (PRL86)

microscopic transport + hydro with phase transition: Still expect Rout/Rside>1

AGS: SPS RHIC

( - time of emission duration)

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). Perfect 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

HBT for direct photonsThe direct photon interferometry is important for investigationof the very early phase of heavy ion collisions. The followingcorrelation function is considerd: (WA98, CERN. M.Aggarwal et al. Phys.Rev.Lett.93 022301(2004))1) The radius Rinv = 5.40.8 fm is near to the one for charged pions.

)]exp(1[)( 222 invinvinv QRAQC

2)The yield of direct photons was extractedfrom the equation 2/ totdir NN

Yield of direct photons versus pT.

The results show dominantcontribution to the hadronic phase of the direct photon emission.

Detection of Upsilons in p-Pb and Pb-p collisions at ALICE muon spectrometer. Analysis of

minibias events. bb̃ BGR & Signal

Pb-p

p-Pb

Analysis ( pt m > 3GeV/c)

bb̃ BGR & Signal

p-Pb

Pb-p

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 AliEn sites in Russia

04Q2 – >4 AliEn operators at work stations

CERN server

INR

IHEP

SPbSU PNPI

KIAE

JINR

ITEP

Brief analysis of currently available data on Physics Data Challenge (2004)

Processed jobs by JINR ~ 2500 (2.0%)

Erroneous jobs on JINR site ~ 404

possible explanation – the RAM capacity of 2 processors batch node (512MB) is insufficient for processing of two AliRoot 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. A. Vodopianov, Status of the ALICE detector (Invited talk),

International Workshop “Quantum Fields and Particles –3”, Baku, September 2004.

2. B.Batyunya, … , S.Zaporozhets. Simulation of ->K+K- detection in ALICE experiment. Presentation on XVII International Seminar on High Energy Physics Problems, Dubna, 2004.

3. 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.

4. 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 2 persons;•Russia 3 persons;•Ukraine 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. 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. 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.