f meson production at 200 gev from star
DESCRIPTION
f meson production at 200 GeV from STAR. Jingguo Ma University of California, Los Angeles for the STAR collaboration. I. Motivations II. Preliminary Results III. Summary. Motivations. m ~ 1019 MeV/c 2 ~ 4.45 MeV/c 2 c t ~ 41 fm Vector meson quark content : s, sbar - PowerPoint PPT PresentationTRANSCRIPT
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production at sqrt(s)=200GeVSQM 2003
meson production at meson production at GeV from STARGeV from STAR
Jingguo MaUniversity of California, Los Angeles
for the STAR collaboration
I. MotivationsII. Preliminary ResultsIII. Summary
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production at sqrt(s)=200GeVSQM 2003
Motivations
Maybe phi can be a good probe of QGP • OZI rule suppression • small cross section for scattering with nonstrange hadrons
•Information from earlier time?•Sensitive to early flow?
Chiral Symmetry Restoration:•mass shift, width broadening?
Production mechanism:•ggg -> •s sbar -> •K+K- ->
• m ~ 1019 MeV/c2
~ 4.45 MeV/c2
• c ~ 41 fm• Vector meson• quark content : s, sbar
• Decay mode: K+ K- (49.2%)
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production at sqrt(s)=200GeVSQM 2003
Data set
Number of charged particles
AuAu collisions: MinBias data 2.1M events Central data(top 5%) 0.5M eventspp collisions: 4M events
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production at sqrt(s)=200GeVSQM 2003
AuAu collisionsMearsured Mass=1019 MeV/c2, FWHM=7.80.5 MeV/c2
K+K- pair invariant mass
background subtracted
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production at sqrt(s)=200GeVSQM 2003
pp collisionsMeasured Mass=1019 MeV/c2, FWHM=7.10.3 MeV/c2
Misidentified KsPhi
K+K- pair invariant mass
background subtracted
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production at sqrt(s)=200GeVSQM 2003
Preliminary resultsPreliminary results
Fit functions:AuAu: mt exponentialpp: pt power law
STAR preliminary|y|<0.5;Measured Pt range:0.4GeV~3.9GeV;Exponential function fit well to the spectra of AuAu collisions;Spectra from pp collisions fit well to a power law function; Statistical errors only.
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production at sqrt(s)=200GeVSQM 2003
Preliminary resultsPreliminary results
AuAu collisions Spectra in different rapidity bins;Exponential function fit to the spectra; Statistical errors only.
STAR preliminary
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production at sqrt(s)=200GeVSQM 2003
dN/dy vs. nCharge
STAR preliminary
• dN/dy increases linearly with nCharge;• Statistical errors only.
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production at sqrt(s)=200GeVSQM 2003
Boost invariance
• Boost invariance in |y|<1.0;• Statistical errors only.
STAR preliminary
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production at sqrt(s)=200GeVSQM 2003
Phi/K-
STAR preliminary
• N()/K- independent of collision centralities.
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production at sqrt(s)=200GeVSQM 2003
Energy dependence
• Data points are from most central heavy ion collisions;• N()/N(h-) increase with beam energy—follow the same trend as the K- production;• Statistical errors only.
STAR preliminary
AGS SPS RHIC
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production at sqrt(s)=200GeVSQM 2003
• Data points are from most central heavy ion collisions;• N()/N(K-) independent of beam energy.
Energy dependence
AGS SPS RHIC
STAR preliminary
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production at sqrt(s)=200GeVSQM 2003
<p<pTT> centrality dependence> centrality dependence
1) , K, p mean transverse momentum <pT> increase in more central collisions;2) Heavier mass particle <pT> increase faster than lighter ones as expected from hydro type collective flow;
Star preliminary
1) , K, p mean transverse momentum <pT> increase in more central collisions;2) Heavier mass particle <pT> increase faster than lighter ones as expected from hydro type collective flow;3) -meson seems flow differently.
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production at sqrt(s)=200GeVSQM 2003
Lines are from thermal model calculation. Again, <pT> of -meson does not change with centrality.-meson may give earlier partonic information!
<p<pTT> vs. particle mass> vs. particle mass
110MeV,<>=0.55
170MeV,<>=0.0
110MeV,<>=0.0
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production at sqrt(s)=200GeVSQM 2003
1) 200 GeV meson production from both AuAu and pp collisions is measured;
2) AuAu spectra fit well to an exponential function, while pp results fit well to a power law function;
3) dN/dy of scales linearly with number of charged particles;
4) dN/dy and inverse slope measurement shows boost invariance for within |y|<1.0;
5) In AuAu collisions, within the measured centrality range, the shape of the transverse momentum distribution weakly depends on the centrality – absence of significant hadronic re-scatterings for phi?
SummarySummary
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production at sqrt(s)=200GeVSQM 2003
Phi/nCharge
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production at sqrt(s)=200GeVSQM 2003
Measured Mass
0-5% 0-10% 10-30%
30-50% 50-80% pp