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Motivation and models Data analysis p+p and Au+Au results Summary

 *(1520) and  *(1385) resonance production in Au+Au and p+p collisions at RHIC energy (200 GeV). Motivation and models Data analysis p+p and Au+Au results Summary. Ludovic Gaudichet SUBATECH, Nantes For the STAR collaboration. Strange Quark Matter 2003.

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Motivation and models Data analysis p+p and Au+Au results Summary

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  1. *(1520) and*(1385) resonance production in Au+Au and p+p collisions at RHIC energy(200 GeV) Motivation and models Data analysis p+p and Au+Au results Summary Ludovic Gaudichet SUBATECH, Nantes For the STAR collaboration Strange Quark Matter 2003

  2. Resonance production in heavy ion collisions Medium effects on resonance and their decay products t hadronization begins Chemical freeze-out Thermal freeze-out • Resonance decay inside the hot and dense medium Mass shift, width broadening, … • Daughter rescattering inside the medium Spectra modification, signal loss, …

  3. Strange hadron resonances and freeze-out within a statistical model Association of at least two resonances could allow the calculation of chemical freeze-out temperature and the interacting phase lifetime between chemical and thermal freeze-out. Including the signal suppression due to freeze-out conditions : The model should take into account resonance regeneration. Giorgio Torrieri and Johann Rafelski Phys.Lett.B509:239-245, 2001

  4. Probing Freeze-out via UrQMD Rescattering probabilities of the resonance decay products are studied. The microscopic study show also a chemical freeze-out followed by a thermal freeze-out. The dynamics is described in term of inelastic and (pseudo)elastic collision rates. Au+Au at 200 GeV Au+Au at 200 GeV UrQMD predicts a relative supression of reconstructable resonances compared to thermal estimation, and a modification of their spectra. Marcus Bleicher and Jörg Aichelin Phys.Lett.B530:81-87, 2002 Marcus Bleicher, private communication

  5. K- p (1520) *(1520) and*(1385) reconstruction in STAR Invariant mass reconstruction *(1520)  p+K- *(1385)  + - *(1385)  + + Combinatorial background reproduced by event mixing. (1385)  *(1520) original mass distribution in p+p - p -

  6. *(1520) in p+p collisions Particle Data Group: Mass: 1519.5 1.0 MeV/c2 Width : 15.6  1.0 MeV/c2 Event mixing technique, (similar results from like sign mixing) and Breit-wigner fit : Anti *(1520) M = 1517 ± 2 MeV /c²  = 26 ± 5 MeV /c² *(1520) M = 1518 ± 2 MeV /c²  = 24 ± 5 MeV /c² STAR preliminary p+p at 200 GeV STAR preliminary p+p at 200 GeV anti-*(1520)/ *(1520) = 0.90 ± 0.11 (not corrected from anti-proton absorption) Same event mixing technique : anti-/ = 0.822 ± 0.008 Yields via bin counting, statistical error only

  7. p+p Mt spectrum  from event mixing, same limited Mt range than  *(1520) STAR preliminary p+p at 200 GeV Exponential fit : *(1520)/ = 0.082 ± 0.007 Only statistic error shown, ~30% systematical error dN/dy = 0.0039 ± 0.0003 slope = 326 ± 42 MeV < Pt > = 0.95 ± 0.07 GeV/c

  8. *(1520) in Au+Au minimum Bias collisions 80% - 60% 60% - 40% M = 1515 ± 3 MeV/c²  = 11 ± 6 MeV/c² • M = 1514 ± 3 MeV/c² • = 21 ± 10 MeV/c² STAR preliminary *(1520)/ratio Measure the yield in the limited Mt range and extrapolate to the dN/dy, assuming a temperature derivated from  results. 10% most central (upper limit) 40%-10% (upper limit) Yields extracted by bin counting, statistical errors only, ~30% sys. uncertainties. <Npart>

  9. pT: 1.2-1.4 GeV Breit-Wigner-Fit + linear BG Mass: 1519.2 1.3 MeV/c2 Width : 12.9  9.6 MeV/c2 preliminary *(1520) Invariant Mass in central Au+Au Collisions pT: 1.0-2.0 GeV 1.7 M events Entries: 17460  6324 extracted via bin counting and subtracting BG fit Acceptance: 35%  5% for y = |0.5| T=350  50 MeV BG uncertainty = 30% of yield thermal model dN/dy = 1.2 preliminary (1520) dN/dy =0.58  0.21  35%

  10. * (1520) over  ratio P.Braun-Munzinger et al, PLB 518 (2001) 41 D. Magestro, private communication     STAR Central point • AuAu min-bias data and central point are consistent. • Suppression of observed lambda*, already in peripheral event • Show the same trend as the K* (Haibin Zhang, Sun)

  11. STAR preliminary *(1385) signal in p+p Sevil Salur, poster session 3 particle event mixing. STAR preliminary p+p at 200 GeV Nentries Nentries Minv (*) [GeV/c²] Minv (*) [GeV/c²] • M(-) = 1321 ± 1 MeV/c² (-)= 5.8 ± 0.7 MeV (gaussian fit) • M(*) = 1381 ± 2 MeV/c² • (*)= 57.5 ± 7.3 MeV (Breit-Wigner) Raw yields : *-+*++*-+*+= 7500 ± 100 (-  + -) & (++ +) = 3000 ± 60 Ratios : / = 0.90± 0.07 */* = 0.89± 0.04 Statistical error is shown. ~20% systematic uncertainty comes from normalization of the background for the yields. Corrected spectra should come soon.

  12. Summary • Clear signal of * (1520) and *(1385) is visible in p+p collisions in STAR data at sNN= 200 GeV. • First results on the production of * (1520) are given in p+p collisions. • * (1520) signal in peripheral minimum bias events of Au+Au collisions is observed in two centrality bins : 80% to 60% and 60% to 40%. *(1520) signal in central data is also consistent with peripheral points. • A comparison of * (1520)/ ratio in p+p and Au+Au collisions shows a decrease of this ratio, already in peripheral Au+Au collisions. This decrease could be explained by the rescattering of daugthers particles between a chemical and thermal freeze-out. • * (1520) and *(1385) resonances could give us a unique chance of probing the rescattering phase of Au+Au collisions and providing information on the collision dynamics.

  13. Embedded Mc (1520) in min-bias AuAu events

  14. Event azymuthal asymmetry effect correction 10% 10% - 40% 40% - 60% 60% - 80% p+p STAR note sn0446

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