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f meson production at 200 GeV from STARPowerPoint Presentation

f meson production at 200 GeV from STAR

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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 Chiral Symmetry Restoration: Production mechanism:

- m ~ 1019 MeV/c2
- ~ 4.45 MeV/c2
- ct ~ 41 fm
- Vector meson
- quark content : s, sbar
- Decay mode:
- K+ K- (49.2%)

- 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?

- mass shift, width broadening?

- ggg ->
- s sbar ->
- K+K- ->

Data set

Number of charged particles

AuAu collisions:

MinBias data 2.1M events

Central data(top 5%) 0.5M events

pp collisions: 4M events

K+K- pair invariant mass

background subtracted

AuAu collisions

Mearsured Mass=1019 MeV/c2,FWHM=7.80.5 MeV/c2

K+K- pair invariant mass

Misidentified Ks

Phi

background subtracted

pp collisions

Measured Mass=1019 MeV/c2, FWHM=7.10.3 MeV/c2

Preliminary results

- |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.

STAR preliminary

Fit functions:

AuAu: mt exponential

pp: pt power law

STAR preliminary

- AuAu collisions Spectra in different rapidity bins;
- Exponential function fit to the spectra;
- Statistical errors only.

dN/dy vs. nCharge

STAR preliminary

- dN/dy increases
- linearly with nCharge;
- • Statistical errors only.

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

Energy dependence

STAR preliminary

• Data points are from most central heavy ion collisions;

• N()/N(K-) independent of beam energy.

AGS

SPS

RHIC

<pT> centrality dependence

1)p, 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;

1)p, 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)f-meson seems flow

differently.

Star preliminary

<pT> vs. particle mass

110MeV,<>=0.55

170MeV,<>=0.0

110MeV,<>=0.0

Lines are from thermal model calculation. Again, <pT> of f-meson does not change with centrality.

f-meson may give earlier partonic information!

Summary

- 200 GeV f meson production from both AuAu and pp collisions is measured;
- AuAu spectra fit well to an exponential function, while pp results fit well to a power law function;
- dN/dy of f scales linearly with number of charged particles;
- dN/dy and inverse slope measurement shows boost invariance for f within |y|<1.0;
- 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?

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