1. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 1 Christina Markert Kent State University Resonance Production in RHIC collisions Motivation Resonance in hadronic phase R AA, elliptic flow v 2 Chiral symmetry restoration (Future plans) Summary for the STAR Collaboration

2. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 2 Why Resonances ? Bubble chamber, Berkeley M. Alston (L.W. Alvarez) et al., Phys. Rev. Lett. 6 (1961) 300. Invariant mass (K 0 +   ) [MeV/c 2 ] K* - (892) 640 680 720 760 800 840 880 920 Number of events 0 2 4 6 8 10 Luis Walter Alvarez 1968 Nobel Prize for “ resonance particles ” discovered 1960 K* from K - +p collision system K    p     p  K      Resonances are: Excited state of a ground state hadron. With higher mass but same quark content. Decay strongly  short life time (~10 -23 seconds = few fm/c ), width = reflects lifetime Can be formed in collisions between the hadrons into which they decay. Why Resonances?: Short lifetime  decay in medium Surrounding nuclear medium may change resonance properties Chiral symmetry restoration: Dropping mass -> width, branching ratio RHIC: No strong indication of medium modification (mass, width) But: Indication of extended lifetime of hadronic medium.  = h/t STAR

3. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 3 Thermal Models Describe Hadronic Yields hadron-chemistry: particle ratios  chemical freeze-out properties T ch ≈ T C ≈ 165 ± 10 MeV Chemical freeze-out ≈ hadronization. s ~ u, d Strangeness is chemically equilibrated. Thermalized system of hadrons can be described by statistical model (mass dependence) ~75% pions ~15% kaons ~10% baryons STAR white paper Nucl Phys A757 (05) 102 Average multiplicity of hadron j (Boltzmann) T chemical

4. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 4 Hadronic Re-scattering and Regeneration Life-time [fm/c] :  (1520) = 13  (1020) = 45 time chemical freeze-out   p       p p signal lost kinetic freeze-out signal measured late decay signal measured re-scattering regeneration [1] Soff et al., J.Phys G27 (2001) 449 [2] M.Bleicher et al. J.Phys G30 (2004) 111 Depends on: hadronic phase density hadronic phase lifetime Regeneration: statistical hadronic recombination UrQMD: Signal loss in invariant mass reconstruction  (1520)  SPS (17 GeV) [1] 50% 26% RHIC (200GeV) [2] 30% 23%

5. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 5  (1520) Results in p+p and Pb+Pb at SPS  (1520)/  in p+p and Pb+Pb C. Markert for the NA49 collaboration, QM2001 NA49 Experiment Fit to NA49 data hep-ph/0310049 [Becattini et al.: hep-ph/0310049] Thermal model does not described  (1520)/  ratio UrQMD: rescattering of decay particle  signal loss in invariant mass reconstruction  (1520) = 50%,  = 26%  Hadronic phase after chemical freeze-out preliminary

6. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 6 Resonance Signals in p+p and Au+Au collisions from STAR K(892)   (1520) p+p Au+Au  (1385) p+p Au+Au  (1020) p+p Au+Au p+p   K(892)  K+   (1232)  p+   (1020)  K + K  (1520)  p + K  (1385)   + 

7. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 7  * and  * show rescattering  * shows regeneration Regeneration/Rescattering cross section:  p)         Interactions of Resonance in Hadronic Nuclear Medium [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] :     Preliminary UrQMD  =10±3 fm/c 

8. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 8 Temperature and “Life-time” from K* and  * (STAR) Model includes: Temperature at chemical freeze-out “Life-time” between chemical and thermal freeze-out By comparing two particle ratios (no regeneration) Lambda1520 T= 160 MeV   > 4 fm/c K(892) T = 160 MeV   > 1.5 fm/c  (1520)/  = 0.039  0.015 at 10% most central Au+Au K*/K - = 0.23  0.05 at 0-10% most central Au+Au G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239 Life time: K(892) = 4 fm/c  (1520) = 13 fm/c

9. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 9 Lifetime of Nuclear Medium T chemical  t > 4 fm/c resonances t ~ 10 fm/c (HBT) Partonic phase  < 6 fm/c C. Markert, G. Torrieri, J. Rafelski, hep-ph/0206260 + STAR  delta lifetime > 4fm/c Lifetime from: Balance function ?

10. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 10 Signal Loss in Low p T Region Inverse slope increase from p+p to Au+Au collisions. UrQMD predicts signal loss at low p T due to rescattering of decay daughters.  Inverse slopes T and mean  p T  are higher. Flow would increase  p T  of higher masse particles stronger.   p T  UrQMD  140 MeV  90 MeV  35 MeV p+p Au+Au K(892) flow  p T  Preliminary

11. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 11 R AA of Resonances (with rescattering) K(892) are lower than K s 0 (and  pt < 2.0 GeV factor of 2 K(892) more suppressed in AA than K s 0

12. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 12 Nuclear Modification Factor R dAu 1.K* is lower than Kaons in low pt d+Au no medium  no rescattering why K* suppression in d+Au ?  * follows h+- and lower than protons.

13. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 13 Mean p T ≠ early freeze-out ? Resonance are regenerating close to kinetic feeze-out  we measure late produced  (1385) How is elliptic flow v 2 effected ?

14. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 14 Resonances v 2 and NCQ Scaling Test Elliptic flow v 2 p T (GeV)  Fluid dynamics calculations (zero viscosity) describe data p T < 2 GeV Do Resonances show same mass splitting ?  Number of Constituent Quark (NCQ) scaling at intermediate p T (2= mesons, 3= baryons)  indication of partonic degrees of freedom Regenerated resonances–final state interactions NCQ = 5 (  * =  +  =3+2) C. Nonaka, et al., Phys.Rev.C69: 031902,2004

15. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 15  elliptic flow v 2 in minbias Au+Au 200 GeV 2(  -  ) dN/d(  -  )  signal Bg of  invmass v 2 =12±2% v 2 =16±0.04%  p T = 1.0-1.5 GeV Inv mass (K + K - ) Elliptic flowReaction plane Kaon p < 0.6 GeV

16. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 16 v 2 of phi resonance in Au+Au 200GeV  has long lifetime 45fm/c  less rescattering or regeneration Elliptic flow of Φ-meson is close to Ks Delta resonance ? STAR Preliminary

17. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 17 Resonance Response to Medium Tc partons hadrons Baryochemical potential (Pressure) Temperature Quark Gluon Plasma ( perfect liquid) Hadron Gas T Freeze Shuryak QM04 Resonances below and above Tc:  Gluonic bound states (e.g. Glueballs) Shuryak hep-ph/0405066  Survival of mesonic heavy quark resonances Rapp et al., hep-ph/0505080  Initial deconfinement conditions: Determine T initial through J/  and  state (+resonance states) dissociation  Chiral symmetry restoration Mass and width of resonances ( e.g.  leptonic vs hadronic decay, chiral partners  and a 1 )  Hadronic time evolution From hadronization (chemical freeze-out) to kinetic freeze-out.

18. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 18 Chiral Symmetry Restoration Ralf Rapp (Texas A&M) J.Phys. G31 (2005) S217-S230 VacuumAt T c : Chiral Restoration Hendrik van Hees (talk) Measure chiral partners Near critical temperature Tc (e.g.  and a 1 ) Data: ALEPH Collaboration R. Barate et al. Eur. Phys. J. C4 409 (1998) a 1  +  TOF cut |1/  -1| < 0.03 STAR: electron hadron separation with Time of Flight upgrade STAR Experiment

19. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 19 Resonances from Jets to Probe Chirality  Bourquin and Gaillard Nucl. Phys. B114 (1976) T=170 MeV,  T  =0 Leading hadrons Medium away near   In p+p collisions resonances are predominantly formed as “leading particles” in jets. Comparison of mass, width and yield of resonances from jets (no medium) with resonances from bulk (medium) jets ?

20. Christina Markert 22 nd Winter Workshop, San Diego, March 2006 20 Summary Hadronic resonances help to separate hadronic from partonic lifetime Ranking of rescattering over regeneration cross section in medium. Low pt R AA behavior confirms rescattering hypothesis. (R dAu puzzle?) v 2 of long lived resonances seems to follow stable particle trends (confirmation of NCQ scaling) Exciting future program: resonance in jets.