The centrality determination The centrality determination for the NICA/MPDfor the NICA/MPD

using the LAQGSM generatorusing the LAQGSM generator

M.BaznatM.Baznat11, K.K.Gudima, K.K.Gudima11, , A.G.LitvinenkoA.G.Litvinenko22, , E.I.LitvinenkoE.I.Litvinenko22

1Institute of Applied Physics, Academy of Science of Moldova, Moldova2JINR Dubna, Russia

The centrality determination – the The centrality determination – the observables:observables:

• The number of particles produced in the region of rapidity close to zero

• The total energy of spectators

22

0

)2(2 RbdbR

geo

The centrality classification

Interval of impact parameter values

Geometrical cross section

fm 42 b

Interval given in percents from the geometrical cross section

% 50 40 Centrality corresponds to the region of the impact parameter:

fm 9.5 )2( 4.0min Rb

fm 10.6 )2( 5.0max Rb

Geometrical cross sectionfor the fixed impact parameter

0.4 )2/(b /)( 2minmin Rb geogeo

0.5 )2/(b /)( 2maxmax Rb geogeo

2

0

2)( bbdbbb

geo

The importance of the centrality study

elliptic flow scaling with space eccentricity

short equlibration time

Jet Quenching – nuclear modification factor vs centrality

At large impact parameters the most of spectator nucleons are bound in fragments.

The NA49 collaboration. Eur. Phys. J., A2, 383, (1998)

Experimental data : the deposited energy for different types of spectators in dependence of

the centrality

Obvious requirements to Obvious requirements to a Zero Degree Calorimeter a Zero Degree Calorimeter

aimed to determine the centralityaimed 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 ZDC for NICA/MPD (standard geometry)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

bpXY

Z

T 1 B

QB0.3Ap

- Ap

zQB0.3cos

QB0.3Ap

)z(y

ApzQB0.3

sinQB0.3Ap

)z(x

T

z

T

z

T

ApzQB0.3

cos12QB0.3Ap

yx )z,B(z

T22

Ap

zQBz

p

pzB

Ap

zQB

zz

T

z

0.3

2

1 ; ),( 0.2

0.3

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

06

zT p/p

LAQGSM high-energy event generatorLAQGSM 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 theINC, followed by evaporation of particles from and/or fission of the compound nuclei.

LAQGSM intranuclear cascade model LAQGSM intranuclear cascade model

The latest improvements of LAQGSM codeThe latest improvements of LAQGSM code

LAQGSM related publicaitonsLAQGSM 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 2008b) 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 pseudorapidityLAQGSM rapidity and pseudorapidity

sqrt(S)=9sqrt(S)=9

sqrt(S)=9sqrt(S)=9

sqrt(S)=5sqrt(S)=5

sqrt(S)=5sqrt(S)=5

URQMD and LAQGSM AuAu mbias data - URQMD and LAQGSM AuAu mbias data - theta:Ekin/Atheta:Ekin/A

URQMD sqrt(S)=9 GeV/u LAQGSM sqrt(S)=9 GeV/u

all nucleonsfree nucleons free nucleons +

fragments

pions pions + …

fragments

LAQGSM AuAu,LAQGSM AuAu, A:bA:b, , Pt/A:Pz/APt/A:Pz/A

Pt/

APz/Ab b

A

Are

st_o

f_pro

ject

ile

Sq

rt(S

)=5

Sq

rt(S

)=9

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

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 nucleonsdirected 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 nucleonsdirected to ZDC

Optimistic results with UrQMD

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 nucleonsand 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 nucleonsand fragments directed to ZDC

Taking into account spectator fragments

All nucleons directed to the hole of ZDC (rectangle 10x10cm2)

0 % - 60 % 60 % - 80 % 80 % - 100 %

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

Interface between mpdroot and LAQGSM Interface between mpdroot and LAQGSM datadata

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);

ConclusionsConclusions• 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 slidesBackup slides

Примеры определения центральности в различных экспериментах

y=0 y=3y>6

STARPHENIXNA49

NA49 ZDC Only

STAR TPC only

PHENIX BBC & ZDC

Study of spectator-nucleons and spectator-fragments Study of spectator-nucleons and spectator-fragments acceptance acceptance

for new ZDC geometryfor new ZDC geometry

Generators: URQMD 1.3 and LAQGSMCollision: mbias (bdb distribution), sqrt(S)=5 (GeV/u), 1000 eventsTransport: Geant3 and Geant4Software framework: mpdrootZDC special geometry: 2 thin layers (0.5mm silicon each) – old and new cross-section

ZDC positions: 287 cm from the collision pointMagnet: the latest geometry for MPD magnetMagnetic field: 0.5 TeslaNo pipeCave material: air

URQMD nucleons (directed and transported to ZDC entrance)

directed to

came to old ZDC came to new ZDCcame to hole

Geant3

Geant4

286182

284772

288372 15639

15520 216888

218084

LAQGSM nucleons (directed and transported to ZDC entrance)

directed to

came to old ZDC came to new ZDCcame to hole

Geant4

79290

?

56673 4944

? ?

38840

LAQGSM fragments (directed and transported to ZDC entrance)

directed to

came to old ZDC came to new ZDCcame to hole

Geant4

23110

?

19680 1425

? ?

14466

GeneratorAll directions: Number of nucleons

Rectangle 90x90 without

hole: Number of nucleons

Rectangle 90x90 with

hole Number of nucleons

Rectangle 10x10

(“hole”): Number of nucleons

URQMD386751 (100%) 301735 (78%) 286182 (74%) 15553 (4%)

LAQGSM387390 (100%) 266997 (69%) 138874 (36%) 128123 (33%)

GeneratorNew 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:ZDC geometry A:(Lead-Scint sandwich: “Lead (Lead-Scint sandwich: “Lead

16mm”)16mm”)

Geometry: cave, magnet, and ZDC (A and B). Cave material: air and vacuum.Magnetic Field: 0 (no field) and 0.5TGenerator: LAQGSM sqrt(S) = 5Transport: Geant4 and Geant3Events: 188

ZDC geometry B:ZDC geometry B:(Scint layer : “Lead 0”)(Scint layer : “Lead 0”)

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

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

Statistical Multifragmentation Model (SMM)Statistical Multifragmentation Model (SMM)

MSDM generator in SHIELD codeMSDM generator in SHIELD code