M.Baznat1, K.K.Gudima1, A.G.Litvinenko2, E.I.Litvinenko2 The centrality determination for the NICA/MPD using the LAQGSM generator M.Baznat1, K.K.Gudima1, A.G.Litvinenko2, E.I.Litvinenko2 1Institute of Applied Physics, Academy of Science of Moldova, Moldova 2JINR Dubna, Russia

The centrality determination – the observables: The number of particles produced in the region of rapidity close to zero The total energy of spectators

The centrality classification Geometrical cross section Geometrical cross section for the fixed impact parameter Interval of impact parameter values Interval given in percents from the geometrical cross section Centrality corresponds to the region of the impact parameter:

Jet Quenching – nuclear modification The importance of the centrality study elliptic flow scaling with space eccentricity short equlibration time Jet Quenching – nuclear modification factor vs centrality

Experimental data : the deposited energy for different types of spectators in dependence of the centrality The NA49 collaboration. Eur. Phys. J., A2, 383, (1998) At large impact parameters the most of spectator nucleons are bound in fragments.

Obvious requirements to a Zero Degree Calorimeter aimed to determine the centrality The calorimeter should measure deposited energy of all types of the spectators: protons, neutrons and nuclear fragments; In order to reach good geometrical acceptance, the calorimeter sensitive areas should be placed to the positions where it is expected to catch the biggest part of the spectators energy; Detailed simulations with the transport of all types of spectators should be performed for each experiment individually taking into account the value and the configuration of magnetic field of the experiment; Event generator for such simulations should produce all types of the spectators with the reasonable yield, and transport code should be able to transport all types of the spectators.

ZDC for NICA/MPD (standard geometry) The technical design of ZDC for NICA/MPD proposed by the group of A.B.Kurepin (INR, Moscow) ZDC consists from the modules 10x10x120cm3 (or 5x5x120cm3) . Each module consists of 60 lead-scintillator sandwiches 10x10cm2 with thicknesses 16 and 4mm. Main attention in the technical design was paid to the method of light readout from the scintillator tiles that should provide good efficiency and uniformity of light collection.

Fast evaluations: the movement of spectators at NICA/MPD The conclusion: Magnetic field of MPD will not change the polar angles for spectators at ZDC position it will only slightly changes the azimutal angles

LAQGSM high-energy event generator LAQGSM describes reactions induced by both particles and nuclei at incident energies up to about 1 TeV/nucleon, generally, as a three-stage process: IntraNuclear Cascade (INC), followed by pre-equilibrium emission of particles during the equilibration of the excited residual nuclei formed after the INC, followed by evaporation of particles from and/or fission of the compound nuclei.

LAQGSM intranuclear cascade model

The latest improvements of LAQGSM code

LAQGSM related publicaitons LAQGSM03.03: a) “CEM03.03 and LAQGSM03.03 Event Generators for the MCNP6, MCNPX, and MARS15 Transport Codes” S. G. Mashnik, K. K. Gudima, R. E. Prael, A. J. Sierk, M. I. Baznat, and N. V. Mokhov, LANL Report LA-UR-08-2931 ; E-print: arXiv:0805.0751v2 [nucl-th] 12 May 2008 b) S. G. Mashnik et al., LANL Report LA-UR-07-6198; E-print: arXiv:0709.173v1 [nucl-th] 12 Sep 2007. c) K. K. Gudima and S. G. Mashnik, Proc. 11th Internat. Conf. on Nuclear Reaction Mechanisms, Varenna, Italy, June 12–16, 2006, edited by E. Gadioli (2006) pp. 525–534; E-print: nucl-th/0607007. LAQGSM03.01: S. G. Mashnik et al., LANL Report LA-UR-05-2686, Los Alamos (2005). LAQGSM: K. K. Gudima, S. G. Mashnik, A. J. Sierk, LANL Report LA-UR-01-6804, Los Alamos, 2001. Quark-Gluon String Model (QGSM): N. S. Amelin, K. K. Gudima, V. D. Toneev, Sov. J. Nucl. Phys. 51 (1990) 327–333; [Yad. Fiz. 51 (1990) 512–523]. Sov. J. Nucl. Phys. 51 (1990) 1093–1101; [Yad. Fiz. 51 (1990) 1730–1743]. Sov. J. Nucl. Phys. 52 (1990) 1722–178, [Yad. Fiz. 52 (1990) 272–282]

LAQGSM rapidity and pseudorapidity sqrt(S)=9 sqrt(S)=9 sqrt(S)=5 sqrt(S)=5

URQMD and LAQGSM AuAu mbias data - theta:Ekin/A URQMD sqrt(S)=9 GeV/u LAQGSM sqrt(S)=9 GeV/u free nucleons + fragments free nucleons all nucleons pions + … pions fragments

LAQGSM AuAu, A:b, Pt/A:Pz/A Sqrt(S)=5 Arest_of_projectile Pt/A Sqrt(S)=9 A b b Pz/A

LAQGSM AuAu, sqrt(S)=9, Pt:Pz per nucleon

Optimistic results with UrQMD URQMD generator, Sqrt(S)=5: all nucleons in 1000 events Total kinetic energy of all nucleons for each URQMD event Total kinetic energy of all nucleons directed to ZDC

Optimistic results with UrQMD URQMD generator, Sqrt(S)=9: all nucleons in 1000 events Total kinetic energy of all nucleons for each URQMD event Total kinetic energy of all nucleons directed to ZDC

Taking into account spectator fragments LAQGSM generator, Sqrt(S)=5: all nucleons in 1000 events Total kinetic energy of all nucleons and fragments for each LAQGSM event Total kinetic energy of all nucleons and fragments directed to ZDC

Taking into account spectator fragments LAQGSM generator, Sqrt(S)=9: all nucleons in 1000 events Total kinetic energy of all nucleons and fragments for each LAQGSM event Total kinetic energy of all nucleons and fragments directed to ZDC

All nucleons directed to the hole of ZDC (rectangle 10x10cm2) 0 % - 60 % 60 % - 80 % 80 % - 100 %

The centrality determination: ZDC (energy) + number of charged barrel tracks

Interface between mpdroot and LAQGSM data Class constructor: MpdLAQGSMGenerator (const char* fileName, const Bool_t use_collider_system=kTRUE); --------------------------------- Class usage in simulation macro: fRun->SetName("TGeant4"); MpdLAQGSMGenerator* guGen= new MpdLAQGSMGenerator(filename); primGen->AddGenerator(guGen);

Conclusions The LAQGSM data can be used for NICA/MPD simulations under mpdroot package based on fairroot software. The LAQGSM angular distributions of the spectators differ from URQMD picture. “The proposed ZDC can measure the centrality alone (without data from another detectors) for the cases when it is known that the impact parameter is smaller than 8 -9 fm. One of the possible solutions is to use the particles multiplicity measured by TPC detector together with the value of energy deposition in ZDC. The selection of the most central and the most peripheral events in this case can be made by the corresponding large and small signal from the TPC. Another solution for the selection of the peripheral events with a small signal in ZDC an additional Zero Degree Neutron (ZDN) calorimeter can be installed after the 1rst dipole magnet of NICA. The selection of the most central and the most peripheral events can also be made by a small electromagnetic calorimeter placed out of the beam in front of ZDC,. The experimental study of the spectator distributions have to be performed on the extracted beam of NUCLOTRON-M at the fixed target. For such study the beam energy equals to (or less than) one NICA ring energy (sqrt(S)=2) is enough.”

Backup slides

Примеры определения центральности в различных экспериментах PHENIX NA49 STAR y=0 y=3 y>6 NA49 ZDC Only STAR TPC only PHENIX BBC & ZDC

Study of spectator-nucleons and spectator-fragments acceptance for new ZDC geometry Generators: URQMD 1.3 and LAQGSM Collision: mbias (bdb distribution), sqrt(S)=5 (GeV/u), 1000 events Transport: Geant3 and Geant4 Software framework: mpdroot ZDC special geometry: 2 thin layers (0.5mm silicon each) – old and new cross-section ZDC positions: 287 cm from the collision point Magnet: the latest geometry for MPD magnet Magnetic field: 0.5 Tesla No pipe Cave material: air

URQMD nucleons (directed and transported to ZDC entrance) came to old ZDC came to hole came to new ZDC Geant3 directed to 284772 15520 216888 286182 Geant4 288372 15639 218084

LAQGSM nucleons (directed and transported to ZDC entrance) came to old ZDC came to hole came to new ZDC directed to ? ? ? 79290 Geant4 56673 4944 38840

LAQGSM fragments (directed and transported to ZDC entrance) came to old ZDC came to hole came to new ZDC directed to ? ? ? 23110 Geant4 19680 1425 14466

All directions: Number of nucleons Generator All directions: Number of nucleons Rectangle 90x90 without hole: Number of nucleons Rectangle 90x90 with hole Number of nucleons Rectangle 10x10 (“hole”): Number of nucleons URQMD 386751 (100%) 301735 (78%) 286182 (74%) 15553 (4%) LAQGSM 387390 (100%) 266997 (69%) 138874 (36%) 128123 (33%) Generator New ZDC + hole: Number of nucleons Hole: Number of nucleons New ZDC: Number of nucleons LAQGSM (p+n+A*fragments) 226640 (100%) 127964 (56.4%) 98676 (43.5%)

ZDC geometry A: (Lead-Scint sandwich: “Lead 16mm”) ZDC geometry B: (Scint layer : “Lead 0”) Geometry: cave, magnet, and ZDC (A and B). Cave material: air and vacuum. Magnetic Field: 0 (no field) and 0.5T Generator: LAQGSM sqrt(S) = 5 Transport: Geant4 and Geant3 Events: 188

LAQGSM AuAu, sqrt(S)=9, Pt/A and theta vs b

LAQGSM Sqrt(S)=9 GeV/u, rapidity

Statistical Multifragmentation Model (SMM)

MSDM generator in SHIELD code