1 / 13

Anthony Timmins for the STAR Collaboration 24th June 2007

The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Au with √s NN = 200 GeV. Anthony Timmins for the STAR Collaboration 24th June 2007. Contents. Motivation The Cu+Cu Dataset  Spectra Comparisons  Spectra Comparisons K 0 Short Spectra Comparisons

tomas
Download Presentation

Anthony Timmins for the STAR Collaboration 24th June 2007

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Auwith √sNN = 200 GeV Anthony Timmins for the STAR Collaboration 24th June 2007

  2. Contents • Motivation • The Cu+Cu Dataset •  Spectra Comparisons •  Spectra Comparisons • K0Short Spectra Comparisons • Integrated Yields vs. <Npart> • The /K0Short Ratio • Summary

  3. MotivationStrangeness Enhancement • For Au+Au 200 GeV, integrated strange particle Yields per Participant, increase with increasing system size. • Can be explained in terms of a phase space/volume effect: • Canonical Suppression… • Curves assume volume  <Npart> • With its differing geometry, recently produced Cu+Cu data should help us understand more about this volume dependency… M. Lamont, SQM 2006

  4. MotivationStrange Baryon/Meson Differences • For Au+Au collisions, increasing mid-pT /K0Short ratios are observed with increasing centrality • Competing particle production mechanisms at mid pT; • Thermal processes more prominent for  • Fragmentation for K0Short • Again, Cu+Cu data may help with the understanding of the system size dependency… M. Lamont, SQM 2006

  5. Cu+Cu sNN = 200 GeV Data Set • Large amount of data taken in 2005: • 55 million events for this analysis •  particles reach pT of 8 GeV/c, K0Short 9 GeV/c • The neutral strange particles are identified via their decay daughters in the STAR TPC • As seen with Au+Au data, the  yields appear to have exponential behaviour up to 5-6 GeV, the K0Short yields up to ~2-3 GeV STAR Preliminary STAR Preliminary

  6. Fit Range Fit Range Spectra Comparisons • Cu+Cu and Au+Au spectra are fit with a Maxwell-Boltzmann at low pT • Au+Au spectra from Phys. Rev. Lett. 98 (2007) 06230 and nucl-ex/0601042 • Each spectra are then divided by the respective fit function • Aim is to access the relative thermal and fragmentation contributions for each system… • Thermal component pushes out further in Cu+Cu for similar <Npart> STAR Preliminary STAR Preliminary • Although Au+Au has slightly larger <Npart>, thermal component more prominent in Cu+Cu at high pT • Despite much bigger Au+Au system, thermal/fragmentation components comparable at high pT

  7. Fit Range Fit Range Spectra Comparisons • Thermal component pushes out further in Cu+Cu for similar <Npart> STAR Preliminary STAR Preliminary • Again, despite much bigger Au+Au system, thermal/fragmentation components comparable at high pT • Although Au+Au has slightly larger <Npart>, thermal component more prominent in Cu+Cu at high pT

  8. Fit Range Fit Range K0Short Spectra Comparisons • Thermal/fragmentation contributions appear similar for both systems... STAR Preliminary STAR Preliminary

  9. Integrated Yields vs. <Npart> • All species show an enhanced production in Cu+Cu… • <Npart> appears not to provide satisfactory scaling for both systems STAR Preliminary STAR Preliminary

  10. STAR Preliminary Cu+Cu 200 GeV STAR Preliminary Cu+Cu <Npart> = 21.2 Au+Au <Npart> = 20.5 Cu+Cu <Npart> = 46.2 Au+Au <Npart> = 61.8 /K0Short Ratio Cu+Cu <Npart> = 98.3 Au+Au <Npart> = 141.4 • Common low pT and high pT values for all systems and centralities • Mid pT ratios don’t scale with <Npart> for the different systems

  11. /K0Short Ratio M. Lamont, SQM 2006 STAR Preliminary • Central /K0Short ratio can be divided by peripheral to give RCP()/RCP(K0Short): • Measure of relative strange baryon/meson difference • Remarkable consistency for different energies. • Add in Cu+Cu with similar C and P: • Consistency extends to the lighter system… • Central <Npart>/Peripheral <Npart> ~ 5 for Cu+Cu and Au+Au at 200 GeV Low and high pT ratios ~ 1

  12. Summary • Enhanced production via thermal processes of strangeness in Cu+Cu • Thermal component of  and  spectra pushes out further in pT •  ,  and K0Short integrated yields per participant are higher • Higher mid-pT/ K0Short ratios in Cu+Cu for similar <Npart> • Suggests that increasing peak is mediated by increasing thermal  production • RCP()/RCP(K0Short) shows remarkable consistency for heavy systems across different energies • This is extended to the Cu+Cu for similar definitions of C and P

  13. Acknowledgements ĎAKUJEM STAR…. University of Illinois at Chicago - Argonne National Laboratory Institute of High Energy Physics - 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 - Creighton University – Nuclear Physics Inst., Academy of Sciences - Laboratory of High Energy Physics - Particle Physics Laboratory - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University Cyclotron Facility - Institut de Recherches Subatomiques de Strasbourg - University of Jammu - Kent State University - Institute of Modern Physics - Lawrence Berkeley National Laboratory - Massachusetts Institute of Technology - Max-Planck-Institut fuer Physics - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University - Panjab University - Pennsylvania State University - Institute of High Energy Physics - Purdue University – Pusan National University - University of Rajasthan - Rice University - Instituto de Fisica da Universidade de Sao Paulo - University of Science and Technology of China - Shanghai Institue of Applied Physics - SUBATECH - Texas A&M University - University of Texas, Austin - Tsinghua University - UNICAMP - Valparaiso University – Variable Energy Cyclotron Centre, Kolkata - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics - Yale University - University of Zagreb

More Related