Patricia Fachini Brookhaven National Laboratory

1. Resonance Production in Au+Au and p+p Collisions at sNN=200 GeV Patricia Fachini Brookhaven National Laboratory Motivation Data Analysis Results Conclusions Patricia Fachini

2. π- ρ0 π+ ρ0 ρ0 ρ0 π- π+ π- ρ0 + + + π+ - - - 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 c = 1.3 fm Φ c = 44 fm Patricia Fachini

3. π K* K K* measured π K* K*lost K π K* π π K* K K K K* measured Chemical freeze-out Kinetic freeze-out Motivation - II • If resonance decays before kinetic freeze-out  not reconstructed due to rescattering of daughters • K*0(c = 4 fm)survival probability timebetween chemical and kinetic freeze-out, source size and pT of K*0 • Chemical freeze-out elastic interactionsπK  K*0πKregenerate 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? Patricia Fachini

4. Resonance Production at RHIC 0(770)π+ π-B.R. ~1 c = 1.3 fm K*0(892) πK 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 KB.R. 0.45 c = 12.6 fm • |y| ≤ 0.5 • Mixed Event or Like Sign Technique Patricia Fachini

5. Raw Invariant Mass Distribution from Data P. Fachini, L. Gaudichet, J. Ma, C. Maguire, H. Zhang SQM2003 Statistical error only p+p p+p 40%-80% Au+Au K*0 STAR Preliminary J. Adams et al. nucl-exp/0307023 J. Adams et al. nucl-exp/0307023 STAR STAR Au+Au p+p Au+Au Φ sNN = 200 GeV STAR Preliminary STAR Preliminary K*0 Φ |y|<0.5 STAR Preliminary p+p 60%-80% Au+Au Au+Au Au+Au PHENIX Preliminary STAR Preliminary STAR Preliminary PHENIX Preliminary ΦK+K- Φe+e- Λ(1520) Λ(1520) Patricia Fachini Invariant Mass (GeV/c2) Invariant Mass (GeV/c2) Invariant Mass (GeV/c2) Invariant Mass (GeV/c2)

6. K*0Mass and Width H. Zhang, SQM2003 STAR Preliminary STAR Preliminary sNN = 200 GeV |y|<0.5 • K*0mass  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 Patricia Fachini

7. Phase Space = π+ ρ0 π+ π- π- -  M2 + pT2 M e T  M2 + pT2 3 Γ(M) Mρ M2– 4mπ2 2 BW(M) = Γ(M) = Γρ (M2 – M2)2+ M2Γ(M)2 Mρ2– 4mπ2 M 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. • 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 emittedT = 120 MeV E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 Patricia Fachini

8. ρ0Mass 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 • ρ0mass ptdependent and lower than previous p+p measurement in both p+p and peripheral Au+Au collisions • ρ0mass high multiplicityp+plower than minimum bias p+p  multiplicity dependent • Systematic errors  common and correlated between p+p and peripheral Au+Au • ρ0width no sensitivity for systematic study 10% of minimum bias p+p for |η|<0.5 sNN = 200 GeV |y|<0.5 Patricia Fachini

9. Mass Shift… • Dynamical Effect E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322; R. Rapp, hep-ph/0305011. • ρ0interactions 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 ρ0decay 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 ρ0mass -38 MeV/c2 shift in the ρ0mass due to t-channel attraction Patricia Fachini

10. Spectra J. Adams et al. nucl-exp/0307023 H. Zhang, SQM2003 J. Ma, SQM2003 P. Fachini, SQM2003 K*0 Φ ρ0 f0 STAR Preliminary STAR Preliminary STAR Preliminary Statistical error only sNN = 200 GeV |y|<0.5 L. Gaudichet, SQM2003 • Au+Au spectra fit to exponential in mT-m0 • p+p  spectra fit to power-law  contribution pQCD processes larger than soft processes ? Λ(1520) pp STAR Preliminary Patricia Fachini

11. Particle Ratios M. Bleicher et al. J. Phys. G 25 (1999) 1859 J. Adams et al. nucl-exp/0307023 P. Fachini SQM2003 J. Ma SQM2003 L. Gaudichet, SQM2003 H. Zhang SQM2003 STAR Preliminary Statistical and systematic errors added in quadrature • Φ/K-independent of centrality Φnot produced via kaon coalescence ? • Cross-section regeneration or rescattering ? Patricia Fachini

12. <pT>Charged Particle Dependence H. Zhang, SQM2003 H. Zhang, SQM2003 J. Ma, SQM2003 J. Ma, SQM2003 Statistical and systematic errors added in quadrature STAR Preliminary STAR Preliminary • Φand K*0  No centrality dependence • Φ Flows differently ? • K*0  Rescattering dominates at peripheral collisions and regeneration becomes significant for central collisions ? Patricia Fachini

13. Λ(1520) Λ f0 ρ0 π- Φ π- K- K*0 K- Thermal Models Chemical freeze-out Kinetic freeze-out Chemical = kinetic freeze-out mρ=770MeV mρ=700MeV sNN = 200 GeV • Short-lived resonances Kinetic freeze-out ? Statistical and systematic errors added in quadrature Patricia Fachini

14. Conclusions • Significantresonanceproduction measured from hadronic interactions from RHIC data at sNN= 200 GeV • ρ0and K*0mass shiftobserved 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 Φnot produced via kaon coalescence ? • Short-lived resonances Regeneration and rescattering driven by hadronic cross sections ? • Resonancescan provide information on the collision dynamics Patricia Fachini