Probing the Medium at RHIC by Identified Particles

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Probing the Medium at RHIC by Identified
Particles
Olga Barannikova, UIC
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Collision Evolution at RHIC
5. Freeze-out
4.Hadronization
3. Thermalization, hydro expansion
2. Pre-equilibrium
1. Initial State
Properties of the medium and hadronization
mechanisms via identified particle measurements
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Outline

• The bulk itself
• Thermalization and extend of success for
  statistical models
• Collectivity in heavy ion collisions (-v2)
• Phase diagram and the energy scan
• The bulk response to jets
• Nuclear modification factors
• The ridge
• PID in jets and ridges
• The early probes
• Charm, beauty

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The Bulk Chemical Composition
Success of Statistical Models describing particle
yields
Chemical equilibration seem to be achieved at
RHIC To what extent? What is the system size
and energy effects? Can we disentangle the
canonical suppression?
Statistical Model results are consistent with
bulk thermalization, indicate u, d, s
equilibration
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Phase Diagram

• Chemical freeze-out
• Tch ?, µB ?
• SIS ? RHIC

1st order
Freeze-out parameters approach Lattice-QCD
phase boundary at SPS energies
F.O. at E ?1GeV per particle
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The Bulk Thermalization?
Blast-wave vs. Hydro
Large flow, lots of re-interactions,
thermalization likely
T. Hirano
A hybrid model QGP fluidhadron gas with Glauber
I.C.
?, K, p ? T 90MeV, b 0.6 c X, ? ? T
160MeV, b 0.45 c
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The Bulk Earlier signals
Multi-strange spectra X, W, ?
Higher Tkin, lower b than p, K, p
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Scaling properties at RHIC
Scaling features
PHOBOS
PHENIX
A. Enokizono
Nch determines the bulk properties?
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The Bulk A Bigger Picture
L. Kumar, SQM2008
Overall smooth systematic with vsNN
NA49 PRC 66 (2002) 054902, PRC 77 (2008)
024903, PRC 73 (2006) 044910
STAR ArXiv 0808.2041, QM2008 E802(AGS)
PRC 58 (1998) 3523, PRC 60 (1999) 044904

E877(AGS) PRC 62 (2000) 024901


E895(AGS) PRC 68 (2003) 054903, PRL
88 (2002) 102301
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Bulk at Freeze-out

• SPS?RHIC smooth systematic behavior of all
  global variables
• Strong increase in radial flow (ltmTgt) from SIS
  to SPS
• Changing trends of freeze-out parameters
  between AGS and SPS
• energies?

T. Nayak
Low energy scan to find the Landmark Critical
End Point
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Search for QCD Critical Point
Energy scan program Is there a Critical Point
in HI Collisions? Signals for onset of
de-confinement? Evolution of medium properties?

• Identified particle studies
• key for success

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Collectivity Above the bulk
v2 - constituent quark scaling

• Mass ordering at low pT -hydro with early
  thermalization

• (Multi-)strange hadron v2 hints the partonic
  origin of collectivity

Hadronization via coalescence?
Pressure gradients converting work into kinetic
energy
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Partonic Flow signals

• (Multi-)strange hadron production v2, spectra,
  ratios consistent with production via
  coalescence of thermalized quarks

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Medium effects Jet quenching

• Strong suppression of hadrons
• No suppression for direct photons

• High pT Color factor effects not
  observed ?, p RAA

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More Scaling RCP
STAR Nucl. Phys. A 757 (2005) 102

• Two groups (2ltpTlt6GeV/c) ?, Ks, K?, K, f ?
  mesons p, ?, ?, O ? baryons

Coalescence or jet-medium effects?
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Jet-induced Baryon Enhancement?
J. Phys. G Nucl. Part. Phys. 34 (2007) S995

• Jet-medium interactions at RHIC
• Rich structures in AuAu data
• Suppression of the Away-side yield
• Broadening/ridge on the Near-side

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Jet chemistry Away-side
Baryon/meson ratios associated with high pT
trigger (pTgt4GeV/c)

• Peripheral ratios vacuum fragmentation
• In-jet ratios inclusive p/(?K)

M.McCumber QM2008
Away-side shoulder study Properties of bulk ?
jet-medium equilibration
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Same-side the Ridge
Production mechanisms

• Jetridge yields follow similar trend in pT for
  all trigger types
• Production mechanisms for jet and ridge are
  different

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Going heavier
Heavy Flavor RHIC

• Binary scaling of total cross-sections
• production via hard processes
• High-pT suppression similar to light hadrons
• indications of quark mass hierarchy

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More on Charm Beauty

• Non-photonic e elliptic flow .
  Sizable v2 saturating at pT2.5GeV/c
• Strong indication for non-zero charm v2

• Spectral measurements support heavy quark
  collectivity
• Evidence of thermalization!
• B. Muller nucl-th/0404015

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Charm or Beauty?
200 GeV pp

• Azimuthal correlations as means for separating.
• Heavy-flavor tagged correlations non-photonic
  electron triggers
• Same-side associate yields expected in B decay
  or fragmentation

Non-photonic electrons - large contribution from
bottom Dominates gt 5GeV?
Suppression, flow, thermalization?
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Production mechanism for J/?
200 GeV pp

• Azimuthal correlations as means for testing.
• Same-side associate yields expected in B decay
  or fragmentation
• Sizable contribution is expected for B?J/?
  pQCD, PYTHIA

• Near side Little or no associated hadron
  production B?J/? doesnt
  dominate inclusive J/?
• Away side Similar to h-h correlation
• away-side from gluon or light
  quark fragmentation

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Summary

• Particle Yields and Spectra major tools for
  experimental study of QCD matter
• Mapping the Phase Diagram
• Studying Thermalization
• Understanding Jet-Medium Interactions
• Color-charge/Quark-flavor Dependencies

• RHIC PID Data
• Intrinsic connection between multiple observables
  -
• Hadron abundances, spectra, flow, angular
  correlations
• High initial density
• Strong interactions partonic collectivity
• Evidence of thermalization