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Resonance production in heavy-ion collisions at STAR

Resonance production in heavy-ion collisions at STAR. Christina Markert University of Texas at Austin. Motivation Resonances Hadronic phase (system size/energy) Chiral symmetry restoration (jets) Conclusion. T chemical. T chemical.

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Resonance production in heavy-ion collisions at STAR

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  1. Resonance production in heavy-ion collisions at STAR Christina Markert University of Texas at Austin • Motivation • Resonances • Hadronic phase (system size/energy) • Chiral symmetry restoration (jets) • Conclusion Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  2. Tchemical Tchemical Lifetime of nuclear medium 200 GeV Au+Au Dt ~ 3-5 fm/c resonances t ~ 10 fm/c 2 particle correlation Partonic phase  ~ 5-7 fm/c Phys. Rev. Lett. 97 (2006) 132301 Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  3. hadronic decay K f signal measured late decay p K p L* K re-scattering signal lost p kinetic freeze-out L* p chemical freeze-out signal measured K K regeneration e+ signal measured early decay f e- leptonic decay time Hadronic re-scattering and regeneration Life-time [fm/c] : K(892) = 4.0 S(1385) = 5.7 L(1520) = 13  (1020) = 45 • Depends on: • hadronic phase density • hadronic phase lifetime Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  4. System size and energy dependence increasing centrality larger system size Au 197 smaller nucleus  Smaller system size compare to number of produced charged particles dN/dy Cu 64 lower energy 200 GeV 62 GeV Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  5. STAR Preliminary STAR preliminary Suppression scales with dNch/dy ~ system size A Lordanova SQM2007 Resonance suppression (system size dependence) [1] P. Braun-Munzinger et.al.,PLB 518(2001) 41, priv. communication [2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81. M. Bleicher and Horst Stöcker J. Phys.G30 (2004) 111. Life-time [fm/c] : K(892) = 4.0 S(1385) = 5.7 L(1520) = 13  (1020) = 45 [1] [2] Regeneration/Rescattering cross section: s(K+p) <s (K+p) < s (L+p) ? L* K* S* Phys. Rev. Lett. 97 (2006) 132301 Phys. Rev. C71 (2005) 064902 See S. Dash SQM2007 statistical errors only ! Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  6. M. Bleicher et al. STAR preliminary STAR preliminary Resonance suppression (energy dependence) Life-time [fm/c] K(892) = 4.0  (1020) = 45 Phys. Rev. C71 (2005) 064902 nucl-ex/0703033 See S. Dash SQM2007 statistical errors only ! • Less re-scattering at lower energies in peripheral collisions • Same volume but, • Lower density  smaller interactions cross section? • Shorter hadronic lifetime  less hadronic interactions ? Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  7. Regeneration might increase elliptic flow minbias 200 GeV Au+Au Recombination model C. Nonaka, et al., Phys.Rev.C69: 031902,2004 Phys. Rev. C71 (2005) 064902 Partonic resonance generation: Number of Constituent Quark (NCQ) scaling at intermediate pT (meson NCQ = 2) Hadronic resonance (re)generation: Regenerated resonances–final state interactions NCQ = 4 (K* = K +p =2+2) Data suggest small regeneration for K* (need smaller errors !) Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  8. Resonance in a medium (nuclear matter) Mass shift and width broadenings are predicted as influence of medium on resonance spectral function, e.g.: For baryonic and strange resonances M.F.M Lutz (SQM 2001) J.Phys.G28:1729-1736,2002 M.F.M Lutz, E.E. Kolomeitsev, Nucl.Phys.A755:29-39,2005. hep-ph/0501224 For mesonic resonances Ralf Rapp (Texas A&M) J.Phys. G31 (2005) S217-S230 L(1520) andS(1385) resonances decay channel change M. Kaskulov et al., nucl-th/0509088 Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  9. away near STAR Preliminary Resonances from jets arXiv:nucl-ex/0706.0724 near-side Df = 0 Df = p Df = p/2 Study Chiral Symmetry Restoration by comparing resonance production in event classes based on azimuthal distribution: We expect high pT resonances from the away side jet to be medium modified due to the high density and temperature of the partonic and pre-equilibrium hadronic medium Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  10. side 1 near away side 2 Formation of hadronic resonances (from jets) in a chiral medium Formation time arguments: a.) General pQCD: Formation time [fm/c] ~ pT [GeV] Formation time [fm/c] ~ 1/mass b.) Specific string fragmentation (PYTHIA) formalism: Gallmeister, Falter, PLB630, 40 (2005) Intermediate pT resonances form early c.) Vitev et al. (hep-ph/0611109): High pT heavy particles and resonances form early Need to determine the right momenta for trigger and resonance particle Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  11. First attempt: f(1020) reconstruction from jets 200 GeV Au+Au charged hadrons Trigger/Event M inv (K+ K-) Number of triggers f(1020) ~95% of events have on trigger particle • Trigger particle: • hadron pT > 4.0 GeV • Associated particle: • resonance f(1020) • <pT>~ 0.9 GeV M inv (K+ K-) Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  12. side1 near away side2 f(1020) from same/away side in/out of plane side1 near - side 51385±2369 61043±2394 Systematic errors are ~ 10% away- side side2 No mass shift or width broadening visible Yield away/same 1.26±0.19 64498±2400 54893±2378 Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  13. Hadron - resonance correlation in Au+Au Df of h-f(1020) – C • h-f(1020) mixed event Hadron trigger pT > 4 GeV f(1020) <pT > ~ 0.9 GeV ( need higher pt ) Not corrected for acceptance Systematic BG normalization error not included STAR preliminary ZYAM = zero yield at minimum Pythia 75M events p+p 200 GeV only phi (no background from K+K combinations) Not corrected for v2 Pythia p+p QM2006 M.Horner Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  14. |1/β-1|<0.03 Time of Flight upgrade detector TOF STAR Experiment • STAR: Time of Flight detector upgrade: • PID at higher momentum • Electron hadron separation • Installation completed in 2-3 years J.WU QM2006 Improves reconstruction of hadronic and leptonic decay channels: K* K+p, Dp+p, L*K+p f K+K, e++e- Christina MarkertSQM2007, June 2007, Levoča, Slovakia

  15. Conclusions • Low momentum resonances provide information regarding the lifetime of hadronic stage. • Re-scattering cross section scales with system size. • Lower collision energy results in less hadronic interactions. • High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration • Need more quantitative theoretical description of formation time of hadronic resonances as a function of mass, momentum and medium density. • First step: Untriggered f(1020) correlation spectrum shows no evidence of medium modification • Next steps: • Trigger on high p Tf(1020) • Reconstruct resonances in jets with shorter lifetime as f(1020) but sufficient statistics (e.g. K*, D). • New TOF detector will help to study higher pT resonance and leptonic decays. Christina MarkertSQM2007, June 2007, Levoča, Slovakia

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