Soft Physics from STAR

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Soft Physics from STAR

• Gene Van Buren
• Brookhaven National Lab
• for the STAR Collaboration
• Quark Matter - July 2002

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(No Transcript)
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Outline of a heavy ion collison

• (Very) Early Stage
• The environment for particle production
• Early-Middle Stages
• QGP?
• Particle production
• partonic
• hadronic
• Late Stage
• Reinteractions of produced hadrons

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Outline of a heavy ion collision
QGP (?) and parton production
hadron reinteraction
pre-collision
hadron production
(very) early environment
dN/dt
time
STAR QM Talk F. Retiere
Chemical freeze out
Collision images S. Bass
Kinetic freeze out
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Initial collisions just like p-p?

• Hard scattering
• Will learn from high-pt studies (not this talk)
• Soft physics
• Effects of nucleons in nuclei
• Multiple interactions (wounded nucleon scaling?)
• Needs understanding from p-A (d-A?)
• Gluon saturation?
• Stopping, leading to net baryons

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STAR B/B Ratios
Ratio systematics versus increasing strange quark
content, and at new energies!
STAR QM Poster on19.6 GeV data D. Cebra
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Energy Evolution of B/B Ratio
Pair-process production is now much larger than
baryon transport!
(ISR)
STAR preliminary
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Centrality evolution of p/p
STAR Preliminary - 200 GeV AuAu
Statistical errors only

• Only a slight decrease with centrality
• Little change in contribution of pair produced
  versus transported baryon number

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Net protons

• Net protons at ycm decreasing with increasing
  energy

130 GeV AuAu
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Charged hadron pt spectra
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dN/dh vs. collision energy
5 central AuAu (PbPb) collisions Phobos PRL
85 (2000) 3100 Phobos nucl-ex 018009
(2002) PHENIX PRL 86 (2001) 3500 STAR(130)
nucl-ex 106004 (2001) BRAHMS QM2001 NA49 WA98
nucl-ex 0008004 (2000) WA97/NA57
CERN-EP-2000-002 E866/917 PRC59 (1999) 2173 E877
PRC51 (1995) 3309
STAR (PRELIMINARY) RESULTS
Phobos
PHENIX
BRAHMS
WA98
Phobos
WA97/NA57
NA49
E917/866
STAR QM Posters on19.6 GeV data D. Cebra 200
GeV data M. Calderon
E877
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ltptgt at 130, 200 GeV
STAR Preliminary

• Similar systematics between the two energies, but
  only a small increase

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ltptgt-scaling (energy)

• Increase is not consistent with expected scaling

STAR systematic error included
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Direct photons p0, h correction
Preliminary
STAR QM Talk I. Johnson
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Direct photons p0 correction
?0 Bose-Einstein Assumption

• Majority of low pt photons from electromagnetic
  decays of pions
• We can address this in STAR

Preliminary
(Ng)p0 Contribution/(Ng)Measured
pt (GeV/c)
STAR QM Talk I. Johnson
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The full spectrum
p/- _at_ 130, 200 GeV
K/-/0s _at_ 130, 200 GeVvia dE/dx and kink PID
STAR Preliminary
STAR QM TalkF. Wang O. Barannikova
STAR Preliminary
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p-, K-, p transverse flow
200 GeVCentral AuAuPreliminary

• New 200 GeV data!
• Confirms trends from 130 GeV spectra get flatter
  with increasing particle mass

p-
K-
p
STAR QM Talk F. Wang O. Barannikova
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Centrality trans. flow buildup
200 GeV AuAu, Preliminary
Antiproton spectra show flattening as collisions
get more and more central.
Antiprotons
STAR QM Talk F. Wang O. Barannikova
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ltptgt systematics (identified particles)
pp ? uncorrected for trigger bias and vertex
finding efficiency
STAR Preliminary
p-
(determined from measured region)
K-
p

• Increases with
• Mass
• Collision energy
• AuAu vs. pp

STAR QM Talk F. Wang O. Barannikova
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and more from 130 GeV
L, L _at_ 130 GeV
p, p _at_ 130 GeV
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Multistrange baryons
Preliminary
STAR Preliminary
STAR QM Talks C. Suire and J. Castillo
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Ratios, experiment vs. a model
Central 130 GeV AuAu Preliminary Data
Agreement between model and data is very good!
STAR Preliminary
Thermal fits to mid-rapidity spectra have caveats
regarding non-4p measurements (local vs. global
equilibrium, boost-invariance). M. Kaneta and
N. Xu, J. Phys. G27 (2001) 589
STAR QM Poster M. Kaneta
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Centrality systematics of chemistry
Fits without (red) and with (blue) X
130 GeV AuAu
STAR Preliminary
STAR QM Poster M. Kaneta
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Where are we?Are we there (yet)?

• Chemical, thermal equilibrium description gives
  high T, low mB
• Consistent with region of phase boundary from
  lattice QCD!
• Similar to early universe!

early universe
Z. Fodor and S.D. Katz nucl-th/0201071
THERMAL MODELS FIT TO RHIC DATA M.
Kaneta, N. Xu P. Braun-Munzinger, D. Magestro,
K. Redlich, J. Stachel W. Broniowski, W.
Florkowski J. Rafelski, J. Letessier
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Rescattering

• Transverse flow
• Approach toward kinetic thermal equilibrium
• Decays in-medium
• (Anti)nuclear coalescence

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Mass dependence of ltpTgt
ltpTgt prediction with Tth and ltbgt obtained from
blast wave model fit
Central AuAu

• X and W show a deviation from common thermal
  freeze-out

ltpTgt GeV/c
ltpTgt prediction with Tth obtained from model fit
but assuming ltbgt0
STAR Preliminary
ltpTgt of X and W from exponential fits in mT
mass GeV/c2
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Rescattering time scales

• Resonances which decays in-medium
• Daughters rescatter, preventing reconstruction
• Leads to suppression of measured yields which may
  be related to time scale for rescattering
• Caveat regeneration of resonances possible?
• Short-lived resonances observed in STAR
• r0(770), w0, h0, K0(892), f0(980) , f0 , D,
  S/-(1385)

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More resonance measurements
pp
AuAu 40 to 80
STAR Preliminary
STAR Preliminary
?sNN 200 GeV
0.2 ? pT ? 0.8 GeV/c y ? 0.5
?0 f0 K0S ? K0
?0 f0 K0S ? K0
0.2 ? pT ? 0.9 GeV/c y ? 0.5
Statistical error only
Statistical error only

• Many resonance states observed
• Some for the first time in heavy ion collisions!

STAR QM Talk P. Fachini
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Sigma(1385)
STAR Preliminary
STAR Preliminary
AuAu 200 GeV minbias
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?0(770) and f0(980) mt spectra
STAR Preliminary
STAR Preliminary
y ? 0.5
Statistical error only
pp
y ? 0.5
AuAu 40 to 80
?0
?0
Statistical error only
200 GeV
STAR Preliminary
STAR Preliminary
Statistical error only
pp
y ? 0.5
y ? 0.5
f0
f0
AuAu 40 to 80
pp ? uncorrected for trigger bias and vertex
finding efficiency
Statistical error only
STAR QM Talks P. Fachini and F. Meissner (UPC)
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f, K0 Measurements
F

• 200 GeV

AuAu Preliminary
AuAu Preliminary
pp Preliminary
STAR QM TalksE. Yamamoto and P. Fachini
pp ? uncorrected for trigger bias and vertex
finding efficiency
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The K0 story
STAR Preliminary
pp ? uncorrected for trigger bias and vertex
finding efficiency

• K0/K suppressed in AA versus pp
• f/K0 appears enhanced versus pp

STAR QM Talks E. Yamamoto and P. Fachini
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Evolution time scale from STAR data
Balance function
?
Chemical freeze out???
Resonance survival
Rout, Rside
Rlong (and HBT wrt reaction plane)
dN/dt
time
1 fm/c
5 fm/c
10 fm/c
20 fm/c
STAR QM Talk F. Retiere
Kinetic freeze out
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Summary

• ltptgt energy dependence does not fit models.
• Hadronic particle yields reveal a statistically
  (chemically equilibrated?) behavior to a high
  degree.
• Hadronic rescattering does little to alter this
  description.
• Net baryons have continued to decrease with
  increasing energy, although theres still some
  stopping/baryon transport to ycm.(But the
  protons are now dominated by those from
  pair-production processes.)
• System is well-described by thermal, chemical
  equilibrium
• High T
• Low mB, net baryons
• An environment similar to moments after the big
  bang, and similar to the conditions of lattice
  QCD calculations! Ripe for QGP production
• Analysis of the data is still in progress much
  more to come!

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STAR Collaboration Institutions
Argonne National Laboratory Institute of High
Energy Physics, Beijing Institute of Physics,
Bhubaneswar University of Birmingham
Brookhaven National Laboratory University of
California, Berkeley University of California,
Davis University of California, Los Angeles
Carnegie Mellon University Creighton
University Laboratory for High Energy (JINR),
Dubna Particle Physics Laboratory (JINR),
Dubna University of Frankfurt Indiana
University, Bloomington Institut de Recherches
Subatomiques, Strasbourg Jammu University
Kent State University Institute of Modern
Physics, Lanzhou Lawrence Berkeley Laboratory
Max-Planck-Instit fuer Physik, Munich Michigan
State University Moscow Engineering Physics
Institute Indian Institute of Technology,
Mumbai City College of New York Ohio State
University Panjab University Pennsylvania
State University Institute of High Energy
Physics, Protvino Purdue University
University of Rajasthan Rice University
Universidade de Sao Paulo University of Science
and Technology of China (USTC) Shanghai
Institue of Nuclear Research (SINR) SUBATECH,
Nantes Texas A M University of Texas,
Austin Tsinghua University Variable Energy
Cyclotron Centre, Kolkata Warsaw University
Warsaw University of Technology University of
Washington Wayne State University Institute
of Particle Physics, Wuhan Yale University