Transcript Document

Joint Institute for Nuclear Research
Analysis of UrQMD Data Obtained for
Relativistic Au+Au Collisions at 17.3 GeV
for STAR detector
F. Nemulodi, M.W. Paradza & D. S. Worku
UCT-CERN Research Centre, University of Cape Town
Supervised by: Dr. Armen Kechechyan, Valery Kizka
Prof. Dr. Mikhail Tokarev
Summer Student Practice, Dubna, 2009
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
Summer Student Practice, Dubna, 2009
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
Summer Student Practice, Dubna, 2009
Spatial & time evolution of heavy ion collisions
ε (GeV/fm3)
• 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.
Tc=170 MeV
Time (fm/c)
pre-equilibrium
initial state
Hadronization,
QGP and
Hydro. expansion mixed phase
high pT
probes,
anisotropy
Hadronic interaction
and chemical freeze-out
particle
ratios
S.Bass.
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Elastic scattering
and kinetic freeze-out
kinetic
freeze out
temperature
Relativistic Heavy Ion Collider, RHIC
3.83 km circumference
Two separated rings
•
120 bunches/ring
•
106 ns bunch crossing time
A+A, p+A, p+p
Maximum 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%
RHIC
Upton, Long Island, New York
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PP2PP
The STAR Detector
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The STAR Detector
MTD
EMC barrel
MRPC ToF barrel
EMC End Cap
Ready for run 10
RPSD
FMS
FPD
TPC
PMD
Complete
Ongoing
DAQ1000
Ready for run 9
HFT
FGT
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R&D
Main goal of investigations in relativistic AA collisions
Search for and study new state of nuclear matter
SPS & NA49
Central Pb-Pb
s1/2=17 GeV
…, AGS, SPS, RHIC, LHC, …
Central Au-Au
s1/2=200 GeV
LHC & ALICE
200 GeV
Cu+Cu 3-6%
Au+Au 35-40%
Central Pb-Pb
s1/2=5500 GeV
RHIC & STAR
…, NICA, FAIR, …
 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.
 What kind of interacting matter is created ?
 Thermodynamics, hydrodynamics, …
 Phase transition, critical point, …
“White papers”
 Self-similarity
of created matter, …
Summer
Student Practice, Dubna,
2009
STAR, PHENIX, PHOBOS &
BRAHMS
AuAu Beam Energy Scan Program at RHIC
Experimental Study of the QCD Phase Diagram and Search for the Critical Point
STAR Run 10 Plan for First Energy Scan
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 Collaboration
B.Abelev et al., Run 10 Beam Energy Scan at RHIC
H.Crawford, AGS-RHIC Meeting, 2009
L.Kumar, SQM08
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Monte Carlo study of AuAu collisions
9.2 GeV
17.3 GeV
AuAu & 9.2 GeV
200 GeV
Central Au-Au
s1/2=200 GeV
?
STAR
RHIC & STAR
Search for location of critical point and clear signatures
of phase transition over a wide kinematical range
(collision energy, size of nucleus, centrality,… )
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Multiplicity distribution in Au-Au at s1/2= 17.3 GeV
UrQMD simulation
>800
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/)

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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
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 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.
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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
Summer Student Practice, Dubna, 2009
 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.
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Energy density & Temperature
System of charged hadrons produced
in AuAu at 17.3 GeV
Energy density
pT distribution
 Bj
m
1 d2 N
= A exp {− T }
2π pT dpT dy
T
0
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
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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.
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Acknowledgements
National Research Foundation of South Africa
Joint Institute for Nuclear Research, Russia
Supervisors:
Dr. Armen Kechechyan, Valery Kizka
Prof. Dr. Mikhail Tokarev
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Thank You for Attention !
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Thank You for Attention !
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Back up slides
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Statistical model
• Statistical model assumes a system
at thermal and chemical equilibrium
described by grand canonical
ensemble.
• Parameters:
• Tchem: chemical freeze out
temperature
• μB and μS: baryon and
strangeness chemical potential
• γS: strangeness supression
factor
200GeV Au-Au
• Stable particle ratios are well
described by statistical model.
http://hep.phy.uct.ac.za/~wheaton/
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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)
Summer Student Practice, Dubna, 2009