1 / 25

First Results from STAR Experiment at RHIC: Soft Hadron Physics Overview

This study presents initial findings from the STAR experiment at the Relativistic Heavy Ion Collider (RHIC), focusing on soft hadron physics. We detail the measurements of various hadrons, including pions, kaons, and protons, and analyze freeze-out conditions through spectra and ratios. Future explorations of p0, resonances, and particle correlations are highlighted. Thermal and chemical freeze-out parameters are discussed in relation to net baryon density and anisotropic flow, suggesting similarities with SPS data but also emphasizing the need for further energy scans.

svea
Télécharger la présentation

First Results from STAR Experiment at RHIC: Soft Hadron Physics Overview

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. First results from STAR experiment at RHIC- Soft hadron physics - Masashi Kaneta for the STAR collaboration Lawrence Berkeley National Lab.

  2. Focus on • Hadrons • Measured : h-, p ±, K±, K0s, K*0, K*0, p, p, d, 3He, 3He, t,L, L, X -, X +, • In future :p 0,f,W -+W -,r, w, h, h’, D, L(1520), S(1385), J/ and more • Freeze-out conditions of low momentum hadrons by • Spectra/Ratios • Thermal/Chemical Freeze-out • Particle correlations • Size parameters, Phase space density • Event anisotropy • v2

  3. Spectra

  4. Spectra • Momentum distributions • Information of thermal (kinetic) freeze-out • The inverse slope parameter of mT distribution reflects temperature and radial flow

  5. Identified particle spectra Only stat. errors are shown Only stat. errors are shown K- 58-85% p 45-58% 26-34% 11-18% K- 6% 58-85% p 45-58% 26-34% 11-18% 6% central collisions  central collisions 

  6. Thermal(Kinetic) freeze-out STAR (sNN=130 GeV) Hydrodynamical model: E. Schnedermann et al. PRC48(1993)2462 mT-mass [GeV/c2] • Thermal freeze-out at RHIC • Temperature is similar at SPS • Larger radial flow than at SPS Inverse slope parameter [GeV/c2] mass [GeV/c2]

  7. Ratios

  8. Ratios • pT dependence anti-particle/particle • Test slope for particle and anti-particle • Anti-baryon/baryon ratio • Stopping or transparent? • Particle ratios from hadrons • Chemical freeze-out parameters

  9. p/p ratio • Minimum bias data • No or weak pT dependence Submitted to PRL Systematic errors<10%

  10. L/L ratio • No significant pT dependence in the ratio • The mean ratio = 0.72±0.04 |y|<0.5 L/L ratio • From 200 K Central trigger Au+Au Events (top ~15% multiplicity.) • Systematic errors are under evaluation

  11. K+/K- ratio ratio STAR Preliminary |y|<0.5 Event fraction = top 7% pT [GeV/c]

  12. Multiplicity dependence of ratios • Not baryon free at mid-rapidity • An effect of anti-baryon absorption in central collisions? L/LPreliminary X+/X-Preliminary p/p submitted to PRL pT 0.6-0.8 GeV/c |y|<0.3 Only statistic errors are shown Systematic errors p/p : 10% L/L and X+/X- : under evaluation ratio (nch/nmax) P e r i p h e r a l  C e n t r a l

  13. Chemical freeze-out 48±12 B 250 Model prediction of ratio LEP/ SppS quarks-gluons RHIC 200 SPS 150 AGS Chemical Temperature Tch [MeV] Experimental ratio 100 SIS 50 hadrons 0 0 200 400 600 800 1000 1200 Baryonic Potential B [MeV]

  14. HBT

  15. HBT Focus in this talk The HBT excitation function Many topics in STAR measurement • Pion HBT • Centrality • Transverse momentum • The HBT excitation function • Phase space density • Event-by-Event HBT • K0s K0s, LL • pp, pp • ppp correlations • Non-identical particles

  16. The HBT excitation function • Compilation 3D -HBT parameters as a function of s • ~10% Central Au+Au(Pb+Pb) events • y ~ 0 • kT0.17 GeV/c STAR Preliminary • No significant jump from SPS to RHIC • We need energy scan between both energy

  17. Event Anisotropy

  18. Event anisotropy • In momentum space • Anisotropy measured as second harmonic parameter v2 • v2 will be scale to initial shape parameter e, if the source has a hydrodynamical expansion Momentum space Almond shape overlap region in coordinate space

  19. Charged particle v2 versus Multiplicity • Boxes show “initial spatial anisotropy”e scaled by 0.19-0.25 PRL 86, (2001) 402 || < 1.3 0.1 < pT < 2.0 nch = primary tracks in || < 0.75

  20. Charged p and p+p, v2(pT) (M.B.)

  21. Comparison with a hydrodynamical model • Hydrodynamical calculations: Huovinen, Kolb and Heinz

  22. Charged particle anisotropy 0<pT<4.5 GeV/c • Minimum bias data • Only statistical errors • Systematic error 10% - 20% for pt = 2 – 4.5 GeV/c

  23. Summary • Net-baryon  0 at mid-rapidity • Anti-baryon/baryon ratios are toward 1, but still <1 • Chemical Freeze-out • Tch : same or higher than at SPS • B：smaller than at SPS • HBT parameters • Similar to SPS • Large anisotropic flow • From mid-central to central data, Hydrodynamical model can describe v2 at low pT (<2GeV/c) • Thermal Freeze-out • Tfo : similar to SPS/AGS • Large radial flow • We need energy scan between SPS and RHIC!

  24. Future plans • TOF • PID up to 2GeV/c of pT • SVT • Increasing momentum resolution • More strangeness baryons • EMC • Electron measurement • Full fields • Higher pT measurement • Increasing momentum resolution • With high statistics • Physics of g, p0, and resonances

  25. g and p0 STAR Preliminary p0 gg invariant mass [GeV] • The e+e- pair from g conversion is measured • Large g acceptance • pT = 50 MeV/c to ~4 GeV/c, |h|<1.8 Typical e+e-pair from g e+ e+ e- e- e- e+ e- e+

More Related