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 0 (1530) in  s NN =200 GeV Au+Au Collisions in STAR

 0 (1530) in  s NN =200 GeV Au+Au Collisions in STAR. Richard Witt for the STAR collaboration. Yale University. Outline. Motivation Data Set Analysis Technique Results Comparisons Conclusions. (Re)Scattering and (Re)Generation.   =  therm -  chem. Time of last scatter

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 0 (1530) in  s NN =200 GeV Au+Au Collisions in STAR

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  1. 0(1530) in sNN=200 GeV Au+Au Collisions in STAR Richard Witt for the STAR collaboration Yale University Outline • Motivation • Data Set • Analysis Technique • Results • Comparisons • Conclusions

  2. Richard Witt – for the STAR Collaboration (Re)Scattering and (Re)Generation  =therm - chem Time of last scatter ~8-10 fm/c Non-resonance ratios fixed * p p F. Retiere and M. Lisa, PRC 70, 044907 (2004) *   K * K*  K   * • Resonances continue to decay • Lifetime < therm for some resonances • Losses due to daughter scattering • Some generation possible • Depends on hadronic • Expect: • suppression of short-lived resonances • enhancement of long-lived resonances • STAR Collaboration PRL 97, (2006) 132301

  3. Richard Witt – for the STAR Collaboration Properties and Data Sets Au+Au @ sNN = 200 GeV 0 to 12%: 7.6 M events 10 to 40%: 5.4 M events 40 to 80%: 6.8 M events • Spin 3/2 multi-strange baryon resonance • Well established (4-star) • Two charge states • only 0(1530) here • 0(1530) ⇒ - + + • Long-lived (c~21 fm) What do we learn? • But... • Small production  • 4-particle final state • Feed-down to -(as much as 40% at 170 MeV) • Letessier and Rafelski, Hadrons and Quark Gluon Plasma, Cambridge, 2002, pg. 34 • Provides another model constraint • Regeneration in Au+Au

  4. Richard Witt – for the STAR Collaboration Rotational Background Subtraction -pT • “Narrow”rotation • Each - pT vector • rotate by 180˚ • take small variations • about rotated vector • mix with all + • Each + pT vector • take small variations • about original direction • mix each with all - +pT 180˚ + all -… + all +… Narrow Method (Au+Au) • Automatically includes v2 • minimizes flow distortions of background

  5. Richard Witt – for the STAR Collaboration Rotational Background Subtraction Breit-Wigner Fit 2/ndf 336.8 / 268  1.531 +/- 0.001  0.015 +/- 0.002 STAR Preliminary Au+Au @ sNN = 200 GeV Background well described Visible signal before subtraction STAR Preliminary Au+Au @ sNN = 200 GeV S / (S+B)  8.6 Mass agrees with PDG ~60% wider (detector resolution)

  6. Richard Witt – for the STAR Collaboration Transverse Momentum Spectra • Measurements in 7 pT bins • out to ~5 GeV/c • 3 centralities • Fit with mT-exponentials • Mid-rapidity yields • scale ~linearly with Npart • same as  STAR Collaboration arXiv:nucl-ex/0606014

  7. Richard Witt – for the STAR Collaboration Mean Transverse Momentum STAR Preliminary • <pT> fits into systematics • p+p points • see arXiv:nucl-ex/0607033 • Inverse Slope • flat with centrality • tracks with -

  8. Richard Witt – for the STAR Collaboration Resonance to Non-Resonance • Ratios (resonance to non) • scaled to central point • short-lived K* suppressed • re-scattering • */ level • (re-) generation • */  suppressed • at creation? • L=2 decay? • */ enhanced • Y. Kanada-En'yo and B. Muller, nucl-th/0608015 • M. Kaskalov and E. Oset, PRC 73, (2006) 045123 • Implication • significant hadronic scattering • density of bath? • large -cross-section?

  9. Richard Witt – for the STAR Collaboration Thermal Model • Thermal model (THERMUS) • ratios at chem • Resonance pattern • suppressed K*/K • level */ • suppressed */  • enhanced */ • suggests significant hadronic scattering

  10. Richard Witt – for the STAR Collaboration Comparison with EPOS • EPOS • arXiv:hep-ph/0603064 • microscopic • partonic interactions • hadronization via string frag. • “Core”: high string density • “Corona”: low string density • Calculations • no normalization • some slope discrepancy For even more * results, see poster 106 by Petr Chaloupka

  11. Richard Witt – for the STAR Collaboration Summary and Conclusions (Thank You!) STAR is the first experiment to have measured the 0(1530) transverse momentum spectra and mid-rapidity yields in heavy-ion collisions. The mid-rapidity yields increase approximately linearly with Npart, <pT> falls within the current systematics. The inverse slopes are approximately constant with centrality Ratios indicate feed-down to - is significant A stronger statement should be possible with statistics on disk and with the p+p point. Pattern of resonance enhancement/suppression with respect to Thermal model calculations suggests significant hadronic scattering A microscopic model, EPOS, also does well at describing the spectra and provides an alernative physics picture

  12. Richard Witt – for the STAR Collaboration The STAR Collaboration Argonne National Laboratory• Institute of High Energy Physics, Beijing• Institute of Physics, Bhubaneswar• University of Birmingham• Brookhaven National Laboratory• California Institute of Technology• University of California, Berkeley• University of California, Davis• University of California, Los Angeles• Carnegie Mellon University• University of Illinois at Chicago• Creighton University• Nuclear Physics Inst., Academy of Sciences• Laboratory for High Energy (JINR), Dubna• Particle Physics Laboratory (JINR), Dubna• University of Frankfurt• Indiana University, Bloomington• Institut de Recherches Subatomiques, Strasbourg• Jammu University• Kent State University• Institute of Modern Physics, Lanzhou• Lawrence Berkeley Laboratory• Massachusetts Institute of Technology • Max-Planck-Instit fuer Physik, Munich• Michigan State University• Moscow Engineering Physics Institute• Indian Institute of Technology, Mumbai• City College of New York• NIKHEF and Utrecht University• Ohio State University• Panjab University• Pennsylvania State University• Institute of High Energy Physics, Protvino• Purdue University• Pusan National University• University of Rajasthan• Rice University• Universidade de Sao Paulo• University of Science and Technology of China (USTC)• Shanghai Institue of Nuclear Research (SINR)• SUBATECH, Nantes• Texas A & M• University of Texas, Austin• Tsinghua University• Valparaiso University• Variable Energy Cyclotron Centre, Kolkata• Warsaw University of Technology• University of Washington• Wayne State University• Institute of Particle Physics, Wuhan• Yale University• University of Zagreb

  13. Richard Witt – for the STAR Collaboration Backups

  14. Richard Witt – for the STAR Collaboration Where in Systematics? • Where is the 0(1530) • what does it tell us? Inline with current systematics? Implications for Hadronic

  15. Richard Witt – for the STAR Collaboration Rotational Background Subtraction Event 1: Au+Au- + + + X Event 2: Au+Au- + + + X … pT pT +pT + all + 60˚ 180˚ + all + + all -   + all + … + all + Isotropic Method (p+p) Narrow Method (Au+Au) • 2 Techniques • Event mixing • Rotation • 2 variations • isotropic • narrow

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