k*(892) resonance production in au+au and cu+cu collisions at s nn = 200 gev & 62.4 gev...
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![Page 1: K*(892) Resonance Production in Au+Au and Cu+Cu Collisions at s NN = 200 GeV & 62.4 GeV Motivation Analysis and Results Summary 1 Sadhana Dash Institute](https://reader031.vdocument.in/reader031/viewer/2022032015/56649cfa5503460f949cb507/html5/thumbnails/1.jpg)
K*(892) Resonance Production in Au+Au and Cu+Cu Collisions at sNN = 200 GeV & 62.4 GeV
Motivation
Analysis and Results
Summary
1
Sadhana DashInstitute of Physics, Bhubaneswar
(For STAR Collaboration)
Outline:
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Neutral K* -meson :
Mass : 896.10 +/- 0.27 MeV Width : 50.70 +/- 0.60MeVDecay Modes : K ~ 100 %Decay Modes for present study K+
K-
BR ~ 66% ……….. Life time : ~ 4 fm Quark Structure : d s d s
Features of K* Meson
2
Charged -meson :
Mass : 891.66 +/- 0.26 MeV Width : 50.80 +/- 0.90 MeVDecay Modes : K ~ 100 %Decay Modes for present study K0
S
K0 S
BR ~ 23% ……….. Life time : ~ 4 fm Quark Structure : K*+ u s K*- u s
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Importance of K* studies
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K*/, /K* information on interplay of rescattering and regeneration effects .
Modification in K* Mass , Width and pT
spectra in-medium dynamical effects
v2 and RCP
measurements of K* provide important information on its production mechanism in the hot/dense phase of heavy ion collisions.
K* lifetime ~4fm/c, sensitive to the properties of hot and dense medium created.
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K* thermally produced at the chemical freeze-out stage
K*lost
K
K*
K*
K K K*
reconstructed
Regeneration Effect compensatesagainst lost K* yield
Chemical freeze-out
Thermal freeze-out
K*
time
K*
K
Daughter particles’ Rescattering Effect destroys part of K* signal
K
Regeneration and Rescattering Effects
4
We study K*/K ratio in p+p and A+A collisions to understand rescattering effect.
K*
reconstructed
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The signal was obtained by subtracting the combinatorialbackground distribution (generated using mixed event technique) from the kaon-pion invariant mass distribution.
K* Invariant Mass Spectrum
0
02
02/4] Signal : Simple Breit-Wigner
5
Background : Linear functionM0 and Gamma
Phys. Rev. C 71 (2005) 064902
MinBiasMinBias
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STAR Time Projection Chamber was used to select kaons and pions.
STAR Experiment
STAR DATA (Run IV & V)Au+Au 62.4 GeV ~ 7e+6 eventsAu+Au 200 GeV ~ 13e+6 eventsCu+Cu 62.4 GeV ~ 10e+6 eventsCu+Cu 200 GeV ~ 8e+6 events
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K*0 Mass and Width Distribution
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K* mass and width are consistent with PDG values
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Centrality Dependence of Transverse Mass Spectra
Exponential Fit function:
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d2N dN/dy 2πmT dmTdy 2 πmT(m0+T)
1exp {-(mT-m0)/T}
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K*0 dN/dy and <pT>
The integrated yields of K* scale with charged particle multiplicityfor Au+Au and Cu+Cu collisions at 62.4 GeV and 200 GeV.
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K* 200GeV (Run II) : Phys. Rev. C 71 (2005) 064902
No significant centrality dependence of <pT> for both Au+Au and Cu+Cu collisions at a given energy.
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There is a suppression of (K*/K-)A+A
/(K*/K-)p+p
ratio with centrality => rescattering effect predominates over regeneration . 10
Rescattering crosssection> 5 times the regeneration cross-section,
Phys. Rev.D 9, 1872(1974)
Particle Ratio (K*/K-)
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(/K*)
A+A/ (/K*)
p+p ratio increases with centrality favouring
rescattering effect: more K* are destroyed than regenerated.
Particle Ratio (Φ/K*)
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Nuclear Modification Factor
Baryon-meson effect is favored in particle production
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Run IV
RCP
of K* is smaller than and K
S at lower p
T => strong
rescattering of daughter particles.
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K* v2
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Scaled particle momentum elliptic flow is same for different species.
Number of quarks is found to be 2.0 +- 0.3 which implies hadronic regeneration process contributes little to the final observed K*
Phys. Rev Lett.92(2004)052302
Number of quarks from v2 scaling = 4 => K*regenerationPhys.Rev.C69 ,031902(2004)
Au+Au at 200 GeV
STAR Preliminary
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K*(896) resonance production has been measured at sNN=62.4 GeV and sNN=200 GeV in both Au+Au and Cu+ Cu collisions by STAR at RHIC.
Measurements of K*0/K and /K*0 ratio, v2, and K* R
CP at low pT are primarily
formed at hadronization.
K*0 integrated yield scales with dNch
/d in both Au+Au and Cu+Cu collision systems.
<pT> shows no significant centrality or system size dependence in Au+Au and Cu+Cu collisions.
Summary
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At intermediate pT , RCP measurements support
baryon -meson effect over mass effect of particle production .A non-zero K* elliptic flow v2 was measured in Au+Au collisions at 200 GeV .
At intermediate pT , the number of quark constituents is found to be 2.0+-0.3 which suppports quark recombination model of particle production.
Summary (contd)
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Typical Invariant Mass Spectrum
The signal was obtained by subtracting the combinatorialbackground distribution (through mixed event technique) from the kaon-pion invariant mass distribution.
0
02
02/4]
Fit function :
0
: K* width
0 : K*
massSTAR PRELIMINARY
Au+Au 62GeV
Signal : Simple Breit-Wigner
Background : Linear functionSTAR PRELIMINARY
18
STAR TPC was used to selectkaons and pions.
STAR DATA (Run IV & V)Au+Au 62.4 GeV ~ 7e+6 eventsAu+Au 200 GeV ~ 13e+6 eventsCu+Cu 62.4 GeV ~ 10e+6 eventsCu+Cu 200 GeV ~ 8e+6 eventsQM-08 Sadhana Dash Jaipur, Feb 04 - 10
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K* <pT> in comparison with other species
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