Analysis of UrQMD Data Obtained for Relativistic Au+Au Collisions at 17.3 GeV

Summer Student Practice, Dubna, 2009

Analysis of UrQMD Data Obtained forRelativistic Au+Au Collisions at 17.3 GeV

for STAR detector

F. Nemulodi, M.W. Paradza & D. S. Worku

Joint Institute for Nuclear Research

Supervised by: Dr. Armen Kechechyan, Valery Kizka Prof. Dr. Mikhail Tokarev

UCT-CERN Research Centre, University of Cape Town


Outline

Introduction (motivation & goals)

Relativistic Heavy Ion Collider (RHIC)

Solenoidal Tracker At RHIC (STAR) Detector

Spatial and time evolution of a nuclear collision

Results of Monte Carlo Simulation for Au+Au collisions

Summary


Motivation & Goals

Study of the deconfined system of strongly interacting quarks and gluons produced in relativistic heavy ion collisions with characterised size more than 1 fm.

Understanding the methods of data analysis in high energy heavy ion physics.

RHIC beam energy scan- Search for critical point- Chiral symmetry restoration


Tc=170 MeV

initial state

pre-equilibriumQGP and

Hydro. expansion

Hadronization,mixed phase

Hadronic interactionand chemical freeze-out

Spatial & time evolution of heavy ion collisions

high pT probes,

anisotropy

particle ratios

• To study the QCD under extreme conditions heavy ion collisions are investigated at relativistic energies.

• A new state of matter is expected to form, reflecting the early universe, few μs after the Big Bang.

Elastic scatteringand kinetic freeze-out

Time (fm/c)

kinetic freeze out

temperature

S.Bass.

ε (G

eV

/fm

3)


Relativistic Heavy Ion Collider, RHIC

3.83 km circumferenceTwo separated rings• 120 bunches/ring• 106 ns bunch crossing timeA+A, p+A, p+pMaximum Beam Energy :• 500 GeV for p+p• 200A GeV for Au+Au Luminosity• Au+Au: 2 x 1026 cm-2 s-1

• p+p : 2 x 1032 cm-2 s-1 Beam polarizations

P=70%

Upton, Long Island, New York

PP2PPRHIC


The STAR Detector


MRPC ToF barrelMRPC ToF barrel

Ready for run 10Ready for run 10

RPSD

PMD

FPD

FMS

EMC barrel

EMC End Cap

DAQ1000DAQ1000

Ready for run 9 FGT

Complete

Ongoing

MTD

R&DHFT

TPC

The STAR Detector


Main goal of investigations in relativistic AA collisions

Search for and study new state of nuclear matter …, AGS, SPS, RHIC, LHC, …

200 GeV

Au+Au 35-40%Cu+Cu 3-6%

Central Au-Au s1/2=200 GeV

RHIC & STAR

High energy-density and very strong interacting matter was created at RHIC. RHIC data on dN /dη , v2 , RCP ,… exhibit scaling laws. Transition to the new state of matter does not manifest abrupt changes in observables.

Central Pb-Pb s1/2=17 GeV

SPS & NA49

LHC & ALICE

Central Pb-Pb s1/2=5500 GeV

What kind of interacting matter is created ? Thermodynamics, hydrodynamics, … Phase transition, critical point, … Self-similarity of created matter, …

“White papers” STAR, PHENIX, PHOBOS & BRAHMS

…, NICA, FAIR, …


AuAu Beam Energy Scan Program at RHIC

Turn off of QGP Signatures and Other New Phenomena

Constituent Quark Number Scaling High & Intermediate pT Spectra: QGP Opacity and the Baryon Anomaly Pair Correlations in ∆φ&∆η Local P violation in Strong Interactions

Search for Phase Transition and Critical Point

Elliptic and Directed Flow Azimuthally Sensitive HBT Fluctuations π/p, K/π, <pT>

STAR CollaborationB.Abelev et al., Run 10 Beam Energy Scan at RHICH.Crawford, AGS-RHIC Meeting, 2009L.Kumar, SQM08

STAR Run 10 Plan for First Energy Scan

Experimental Study of the QCD Phase Diagram and Search for the Critical Point


STAR

AuAu & 9.2 GeVCentral Au-Au s1/2=200 GeV

RHIC & STAR

Monte Carlo study of AuAu collisions

?

9.2 GeV 17.3 GeV 200 GeV

Search for location of critical point and clear signatures of phase transition over a wide kinematical range (collision energy, size of nucleus, centrality,… )


Multiplicity distribution in Au-Au at s1/2= 17.3 GeV

11000 events & 3 centrality classes: 0-10%, 10-30%, 30-60 %. Usage of UrQMD code to generate events and obtain data sample for analysis (http://th.physik.uni-frankfurt.de/~urqmd/)

UrQMD simulation

>800


pT spectra of charged particles in AuAu

exponential behavior pT< 2 GeV/c

a power behavior pT >2 GeV/c

the centrality dependence of spectra


Data sample were generated using MC UrQMD code.

11000 events were generated.

Data were analyzed in ROOT framework (http://root.cern.ch/)

pT spectra of hadron species produced in Au+Au collisions at different centralities were obtained.


Rapidity distributions of charged hadrons

Smooth behavior of a multiplicity density vs. rapidity y.

Width of the dN/dy decreases as centrality increases.

*) arbitrary scaling factor


Data sample were generated using MC UrQMD code.

11000 events were generated.

Data were analyzed in ROOT framework (http://root.cern.ch/)

Rapidity distribution of hadron species produced in Au+Au collisions at different centralities were obtained.


Energy density & Temperature

12π pT

d 2NdpT dy

= A exp {−mTT

}

System of charged hadrons produced in AuAu at 17.3 GeV

Energy density pT distribution

Centrality Energy density(GeV/fm3)

Temperature (MeV)

min.bias 6.0 ± 0.1 198.8 ± 0.2

0-10% 12.8 ± 0.6 203.1 ± 0.2

10-30% 7.4 ± 0.3 200.9 ± 0.3

30-60% 3.1± 0.5 194.5 ± 0.4

0

Bj


Summary

Monte Carlo study of Au-Au collisions at the energy 17.3 GeV using UrQMD generator in the ROOT framework was performed.

Monte Carlo data sample for Au-Au collisions was analyzed. Rapidity distribution of produced pions, kaons, protons and antiprotons at different centralities were obtained.

Transverse momentum spectra of pions, kaons, proton and antiprotons at different centralities were obtained.

Temperature and energy density values for system consisted of charged hadrons with respect to each centrality classes were estimated.

Higher statistics of generated MC events is necessary for comparison with future STAR data.


National Research Foundation of South Africa

Joint Institute for Nuclear Research, Russia

Supervisors:

Dr. Armen Kechechyan, Valery Kizka

Prof. Dr. Mikhail Tokarev

Acknowledgements


Thank You for Attention !


Back up slides


Statistical model

• Stable particle ratios are well described by statistical model.

http://hep.phy.uct.ac.za/~wheaton/

• Statistical model assumes a systemat thermal and chemical equilibrium described by grand canonical ensemble.

• Parameters:

• Tchem: chemical freeze outtemperature• μB and μS: baryon and strangeness chemical potential• γS: strangeness supression factor

200GeV Au-Au


Spatial evolution of a heavy ion collision

Lorenz contracted heavy ions approaching..

relativistic speeds cause the ions to appear disk –like

Ions interpenetrates, individual particles scatter

Deconfined quarks and gluons, plasma forms:- very short –lived, not observable

Formation of hadrons observable particles, analysis of this reveals information about QGP (quark gluon plasma)

Analysis of UrQMD Data Obtained for Relativistic Au+Au Collisions at 17.3 GeV

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