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. m ~ 1019 MeV/c 2  ~ 4.45 MeV/c 2 c t ~ 41 fm Vector meson quark content : s, sbar

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f meson production at 200 GeV from STAR

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F meson production at 200 gev from star

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

Motivations

  • 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?

  • Chiral Symmetry Restoration:

    • mass shift, width broadening?

  • Production mechanism:

    • ggg -> 

    • s sbar -> 

    • K+K- -> 


  • Data set

    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

    K+K- pair invariant mass

    background subtracted

    AuAu collisions

    Mearsured Mass=1019 MeV/c2,FWHM=7.80.5 MeV/c2


    K k pair invariant mass1

    K+K- pair invariant mass

    Misidentified Ks

    Phi

    background subtracted

    pp collisions

    Measured Mass=1019 MeV/c2, FWHM=7.10.3 MeV/c2


    Preliminary results

    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


    F meson production at 200 gev from star

    Preliminary results

    STAR preliminary

    • AuAu collisions Spectra in different rapidity bins;

    • Exponential function fit to the spectra;

    •  Statistical errors only.


    Dn dy vs ncharge

    dN/dy vs. nCharge

    STAR preliminary

    • dN/dy increases

    • linearly with nCharge;

    • • Statistical errors only.


    F meson production at 200 gev from star

    Boost invariance

    STAR preliminary

    • Boost invariance in |y|<1.0;

    • • Statistical errors only.


    Phi k

    Phi/K-

    STAR preliminary

    • N()/K- independent of collision centralities.


    Energy dependence

    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 dependence1

    Energy dependence

    STAR preliminary

    • Data points are from most central heavy ion collisions;

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

    AGS

    SPS

    RHIC


    P t centrality dependence

    <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


    P t vs particle mass

    <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

    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?


    Phi ncharge

    Phi/nCharge


    F meson production at 200 gev from star

    0-5% 0-10% 10-30%

    30-50% 50-80% pp

    Measured Mass


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