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

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

3. 3Richard Witt – for the STAR Collaboration Properties and Data Sets 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) 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 What do we learn? 0 to 12%: 7.6 M events 10 to 40%: 5.4 M events 40 to 80%: 6.8 M events Au+Au @  s NN = 200 GeV

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

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

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

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

8. 8Richard Witt – for the STAR Collaboration Resonance to Non-Resonance 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? Ratios (resonance to non) scaled to central point short-lived K* suppressed re-scattering  */  level (re-) generation  */  suppressed at creation? L=2 decay?  */  enhanced

9. 9Richard 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. 10Richard 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. 11Richard Witt – for the STAR Collaboration 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 N part, 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 Summary and Conclusions (Thank You!)

12. 12Richard Witt – for 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 The STAR Collaboration

13. 13Richard Witt – for the STAR Collaboration Backups

14. 14Richard 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. 15Richard Witt – for the STAR Collaboration Rotational Background Subtraction Event 1: Au+Au   - +  + + X Event 2: Au+Au   - +  + + X … 2 Techniques Event mixing Rotation 2 variations isotropic narrow  pT pT 60˚ + all  +  Isotropic Method (p+p) Narrow Method (Au+Au)  pT pT 180˚ + all  + … + pT+ pT + all  - 