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Patricia Fachini 1STAR
Patricia FachiniBrookhaven National
LaboratoryMotivation
Data AnalysisResults
Conclusions
Resonance Production in Au+Au and p+p Collisions at sNN=200 GeV
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Patricia Fachini 2STAR
Motivation - I • In-medium modification of mass and/or width Chiral Symmetry
Restoration, Collision Broadening or Phase Space?
• ρ0(770) Leptonic decay channel probes all stages of the collision. Hadronic decay channel probes only late stages of the collision
• Φ Information from early time ? • f0(980) KK molecule (bound state) insight strangeness
behavior in relativistic collisions• K*0(892) Regeneration and daughter rescattering time scale ?
ρ0 ρ0π-
π+
π+
π-
ρ0 c = 1.3 fm
ρ0
ρ0
+
+
-
-
π- π+
ρ0
-
+
Φ c = 44 fm
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Patricia Fachini 3STAR
Motivation - II • If resonance decays before
kinetic freeze-out not reconstructed due to rescattering of daughters
• K*0 (c = 4 fm) survival probability time between chemical and kinetic freeze-out, source size and pT of K*0
• Chemical freeze-out elastic interactions πK K*0 πK regenerate K*0(892) until kinetic freeze-out
• K*0/K may reveal time between chemical and thermal freeze-out
• Λ*/Λ, ρ0/π, f0/π ?
Chemical freeze-out
Kinetic freeze-out
K*
lost
K*
measuredπ
π
K
K*K
K*
K*
π
K
ππK*
K K K*
measured
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Patricia Fachini 4STAR
0(770) π+ π- B.R. ~1 c = 1.3 fm
K*0(892) π K B.R. 2/3 c = 4 fm
f0(980) π+ π- B.R. 2/3 c = 2.6 fm
Φ(1020) K+ K- B.R. 0.492 c = 44 fm
Φ(1020) e+ e- B.R. 0.000296 c = 44 fm
Λ(1520) p K B.R. 0.45 c = 12.6 fm
• |y| ≤ 0.5
• Mixed Event or Like Sign Technique
Resonance Production at RHIC
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Patricia Fachini 5STAR
Raw Invariant Mass Distribution from Data P. Fachini, L. Gaudichet, J. Ma, C. Maguire, H. Zhang SQM2003
Invariant Mass (GeV/c2) Invariant Mass (GeV/c2) Invariant Mass (GeV/c2) Invariant Mass (GeV/c2)
p+p
p+p Au+Au
Au+Au Au+Au
STAR Preliminary
STAR Preliminary
STAR Preliminary
PHENIX Preliminary PHENIX Preliminary
K*0
Φ
Φ
ΦK+K- Φe+e-
Statistical error only
J. Adams et al. nucl-exp/0307023
STAR
p+p 40%-80% Au+Au
J. Adams et al. nucl-exp/0307023
STAR
K*0
STAR Preliminary
|y|<0.5
sNN = 200 GeV
Au+Au
STAR Preliminary
Λ(1520)
p+p 60%-80% Au+AuSTAR Preliminary
Λ(1520)
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Patricia Fachini 6STAR
K*0 Mass and Width
• K*0 mass shifted in p+p and Au+Au at low pT
• K*0 width agrees with the MC (GEANT) calculation• Systematic and statistical error added in quadrature
H. Zhang, SQM2003
STAR PreliminarySTAR Preliminary
|y|<0.5
sNN = 200 GeV
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Patricia Fachini 7STAR
Phase Space
P. Braun-Munzinger et.al., CERES Int. Note, March 2000, unpublished; E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322; P.K. Kolb and M. Prakash, nucl-th/0301007; H.W. Barz et al., Phys. Lett. B 265, 219 (1991); R. Rapp, hep-ph/0305011.
ρ0
π-
π+
π-
π+
• M = Invariant Mass; pT = transverse momentum; T = Temperature
• pp particle composition reasonably reproduced by statistical model T = 160 MeV
F. Becattini, Nucl. Phys. A 702, 336 (2002); Z. Phys. C 69, 485 (1996); F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997)
• Au+Au between chemical and kinetic freeze-out resonances formed until particles too far apart resonances emitted T = 120 MeV
E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322
e- M2 + pT
2
TM
M2 + pT2
Phase Space =
BW(M) = Γ(M)
(M2 – M2)2 + M
2 Γ(M)2
Γ(M) = Γρ
M2 – 4mπ2
Mρ2 – 4mπ
2
32 Mρ
M
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Patricia Fachini 8STAR
ρ0 Mass J. Adams et al. nucl-exp/0307023
• p+p at s = 27.5 GeV M = 762.6 ± 2.6 MeV/c2
• PDG average hadroproduced ρ0
M = 769.0 ± 0.9 MeV/c2
• PDG average e+e- ρ M = 775.9 ± 0.5 MeV/c2
• ρ0 mass pt dependent and lower than previous p+p measurement in both p+p and peripheral Au+Au collisions
• ρ0 mass high multiplicity p+p lower than minimum bias p+p multiplicity dependent
• Systematic errors common and correlated between p+p and peripheral Au+Au
• ρ0 width no sensitivity for systematic study
10% of minimum bias p+p for |η|<0.5
|y|<0.5
sNN = 200 GeV
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Patricia Fachini 9STAR
Mass Shift…
• Dynamical Effect E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322; R. Rapp, hep-ph/0305011.
– ρ0 interactions at late stages of the collision• nucleons, hyperons and baryon resonances• pions, kaons and ρ0-mesons• t-channel exchanges
Distortion of the ρ0 spectral shape mass shift and/or broadening
• Interference between various π+π- scattering channels R. Longacre, nucl-exp/0305015
• Bose-Einstein correlations between ρ0 decay daughters and pions in the surrounding matter G.D. Lafferty, Z. Phys. C 60, 659 (1993); R. Rapp, hep-ph/0305011; S. Pratt et al., nucl-th/0308087.
-23 MeV/c2 shift in the ρ0 mass
-38 MeV/c2 shift in the ρ0 mass due to t-channel attraction
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Patricia Fachini 10STAR
Spectra
• Au+Au spectra fit to exponential in mT-m0
• p+p spectra fit to power-law contribution pQCD processes larger than soft processes ?
P. Fachini, SQM2003 J. Adams et al. nucl-exp/0307023
L. Gaudichet, SQM2003
STAR Preliminary
Λ(1520)
pp
ρ0
f0
Φ
J. Ma, SQM2003
STAR Preliminary
H. Zhang, SQM2003
K*0
STAR Preliminary
Statistical error only
STAR Preliminary
sNN = 200 GeV|y|<0.5
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Patricia Fachini 11STAR
• Φ/K- independent of centrality Φ not produced via kaon coalescence ?
• Cross-section regeneration or rescattering ?
M. Bleicher et al. J. Phys. G 25 (1999) 1859
Particle Ratios
STAR Preliminary
J. Adams et al. nucl-exp/0307023 H. Zhang SQM2003L. Gaudichet,
SQM2003 J. Ma SQM2003
P. Fachini SQM2003
Statistical and systematic errors added in quadrature
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Patricia Fachini 12STAR
• Φ and K*0 No centrality dependence• Φ Flows differently ?• K*0 Rescattering dominates at peripheral collisions and
regeneration becomes significant for central collisions ?
H. Zhang, SQM2003 J. Ma, SQM2003 H. Zhang, SQM2003 J. Ma, SQM2003
STAR Preliminary
STAR Preliminary
<pT> Charged Particle DependenceStatistical and systematic errors added in quadrature
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Patricia Fachini 13STAR
Thermal Models
• Short-lived resonances Kinetic freeze-out ?
Chemical freeze-out
Kinetic freeze-out
Chemical = kineticfreeze-out
mρ=700MeV
mρ=770MeV
f0
π-
ρ0
π-
K*0
K-
ΦK-
Λ(1520)Λ
Statistical and systematic errors added in quadrature
sNN = 200 GeV
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Patricia Fachini 14STAR
• Significant resonance production measured from hadronic interactions from RHIC data at sNN = 200 GeV
• ρ0 and K*0 mass shift observed even after phase space correction in p+p and Au+Au collisions
• Lower mass expected due to in-medium modifications, interference and Bose-Einstein correlations ?
• Φ/K- independent of centrality Φ not produced via kaon coalescence ?
• Short-lived resonances Regeneration and rescattering driven by hadronic cross sections ?
• Resonances can provide information on the collision dynamics
Conclusions