1 / 15

Strange and Non-Strange Particle Ratios as a Function of p T and centrality in STAR at RHIC

Strange and Non-Strange Particle Ratios as a Function of p T and centrality in STAR at RHIC. B. Norman, Kent State University, and the STAR Collaboration. Outline. Physics Motivation Particle identification Topological ID of K +/- (kinks) Ring Imaging CHerenkov detector (RICH)

ina
Télécharger la présentation

Strange and Non-Strange Particle Ratios as a Function of p T and centrality in STAR at RHIC

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. Strange and Non-Strange Particle Ratios as a Function of pTand centrality in STAR at RHIC B. Norman, Kent State University, and the STAR Collaboration

  2. Outline • Physics Motivation • Particle identification • Topological ID of K+/- (kinks) • Ring Imaging CHerenkov detector (RICH) • Charged Kaons • K-/K+ ratio • High pT behavior • Particle Ratios • p/p, L/L • Model agreement

  3. Physics Motivation • Particle ratios probe: • Strangeness enhancement • K/p ~ s/d, s/d • Net baryon density • p/p, L/L ~ u/u, d/d • Gluon / Quark fragmentation regimes • p/p , L/L ~ glue/(quark + glue) • Medium opacity • K/p, p/p , L/L, RAA

  4. Traditional V0-like analysis with DCA cuts and kinematic analysis Kink PID For example, Kaon decays: K →m + n K+/- → π+/- + π0 Pion contamination: π →m + n Kinks = one prong decays

  5. Efficiency = Nfound / Ndecayed Acceptance = Ndecayed / Ntotal K- efficiency & acceptance

  6. STAR 200 GeV Au-Au PRELIMINARY Kink K- (|y|<0.5) dE/dx K- (|y|<0.1) Kinks dramatically increase momentum range of identified Kaons

  7. RICH PID Allows identification of particles to much higher momentum than dE/dx measurements in the TPC. 1 < p < 3 GeV/c for K+-, p+- 1.5 < p < 5 GeV/c for p, p

  8. dE/dx STAR p+p Kinks STAR 200 GeV Au-Au PRELIMINARY K-/K+ SPS/NA49 Very little dependence of K-/K+ ratio on centrality AGS/E866 dNp-/dy

  9. High momentum charged Kaons do not seem to follow a simple thermal (exponential) trend. They are more consistent with a (pQCD-inspired) power law. STAR 200 GeV Au-Au PRELIMINARY

  10. Little pT dependence: any high pT effects are present in both charges STAR 200 GeV Au-Au PRELIMINARY

  11. TPC de/dx RICH Systematic decrease in baryon/anti-baryon ratio with pT begins fairly early, not seen in the Kaons. STAR 200 GeV Au-Au PRELIMINARY

  12. Decrease in AntiBaryon/Baryon ratio at low (2-3 GeV/c) pT in agreement with pQCD predictions Onset of quark-dominated production??? p/p soft+quench

  13. If no “effects”: R < 1 in regime of soft physics R = 1 at high-pt where hard scattering dominates High pT K+- suppression • Nuclear modification factor RAA measures how AA spectra scales relative to pp. • Using only Au-Au data, we can approximate RAA using peripheral collision data, which have similar features to p-p (i.e., they scale with the number of binary collisions at higher momenta)

  14. STAR 200 GeV Au-Au PRELIMINARY Binary Collision Scaling K+ +K- N Participant Scaling 0-5% / 40-60% centrality 0-5% / 60-80% centrality Central charged Kaons show systematic suppression at high pT consistent with other particle spectra. (See Hui Long’s STAR talk) Suppression may be due to partonic energy loss?

  15. Conclusions • Baryon/anti-baryon ratios decrease at higher pT: not inconsistent with the trend of pQCD • Charged Kaons exhibit strong suppression at high pT in central data, a common trend in hadrons at RHIC.

More Related