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 The quark gluon liquid - an unexpected phase of matter. As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons. If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons. Let me describe this state with the conclusion of my talk. Christina Markert SQM2007, June 2007, Levoča, Slovakia

Lifetime of nuclear medium 200 GeV Au+Au Tchemical 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 Markert SQM2007, June 2007, Levoča, Slovakia

Hadronic re-scattering and regeneration time signal lost signal measured late decay early decay chemical freeze-out f L* p K kinetic freeze-out re-scattering regeneration e+ e- leptonic decay hadronic decay 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 Markert SQM2007, June 2007, Levoča, Slovakia

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 Markert SQM2007, June 2007, Levoča, Slovakia

Resonance suppression (system size dependence) Suppression scales with dNch/dy ~ system size STAR preliminary [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. STAR Preliminary A Lordanova SQM2007 Life-time [fm/c] : K(892) = 4.0 S(1385) = 5.7 L(1520) = 13  (1020) = 45 [1] [2] Phys. Rev. Lett. 97 (2006) 132301 Phys. Rev. C71 (2005) 064902 Regeneration/Rescattering cross section: s(K+p) < s (K+p) < s (L+p) ? L* K* S* See S. Dash SQM2007 statistical errors only ! Christina Markert SQM2007, June 2007, Levoča, Slovakia

Resonance suppression (energy dependence) STAR preliminary M. Bleicher et al. STAR preliminary 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 Markert SQM2007, June 2007, Levoča, Slovakia

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 Markert SQM2007, June 2007, Levoča, Slovakia

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) and S(1385) resonances decay channel change M. Kaskulov et al., nucl-th/0509088 Christina Markert SQM2007, June 2007, Levoča, Slovakia

Resonances from jets arXiv:nucl-ex/0706.0724 STAR Preliminary near away near-side Df = 0 Df = p Df = p/2 The quark gluon liquid - an unexpected phase of matter. As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons. If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons. Let me describe this state with the conclusion of my talk. 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 Markert SQM2007, June 2007, Levoča, Slovakia

Formation of hadronic resonances (from jets) in a chiral medium side 1 side 2 near away 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 Low pt High pt Near side No medium or late hadronic medium No medium Away side Late hadronic medium Partonic or early hadronic medium (depend on formation time) CSR ? Side 1 & 2 Late hadonic medium Early hadronic medium The quark gluon liquid - an unexpected phase of matter. As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons. If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons. Let me describe this state with the conclusion of my talk. Need to determine the right momenta for trigger and resonance particle Christina Markert SQM2007, June 2007, Levoča, Slovakia

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 Markert SQM2007, June 2007, Levoča, Slovakia

f(1020) from same/away side in/out of plane near - side side1 side1 side2 near away 51385±2369 61043±2394 away- side Systematic errors are ~ 10% side2 No mass shift or width broadening visible Yield away/same 1.26±0.19 64498±2400 54893±2378 Christina Markert SQM2007, June 2007, Levoča, Slovakia

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 Markert SQM2007, June 2007, Levoča, Slovakia

Time of Flight upgrade detector TOF |1/β-1|<0.03 STAR: Time of Flight detector upgrade: PID at higher momentum Electron hadron separation Installation completed in 2-3 years STAR Experiment 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 Markert SQM2007, June 2007, Levoča, Slovakia

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 T f(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 Markert SQM2007, June 2007, Levoča, Slovakia