Soft-hadron Physics at RHIC Results from the Relativistic Heavy Ion Collider (Part II)

1. Soft-hadron Physics at RHICResults from the Relativistic Heavy Ion Collider (Part II) First joint Meeting of the Nuclear Physics Divisions of APS and JPS Maui, Hawaii, 2001 Oct. 19 / Masashi Kaneta LBNL MKaneta@lbl.gov http://www.rhic.bnl.gov/~kaneta/ Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

2. 3 Years ago, in JPS meeting • Summary of SPS results by M.K. Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

3. Outline • Introduction • Particle ratios / yield • Identified single particle spectra • Event anisotropy • Particle correlation (HBT) • Summary • Open issues Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

4. Introduction Thermal freeze-out Chemical freeze-out hadron parton A A • Goal • Study bulk properties of matter under extremely high energy and particle density • Information of observable come from Parton / hadron level time elastic interaction inelastic interaction space • Focus of this talk • Low pT and mid-rapidity data Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

5. Particle ratios/yield • Anti-baryon/baryon ratio and net-proton • Stopping or transparent? • Particle ratios from hadrons • Chemical freeze-out parameters Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

6. Anti-Baryon/Baryon ratio • B/B <1 • Not baryon free • Less centrality • dependence L/L ratio STAR PRL86 (2001) 4778 130 GeV RHIC : STAR / PHENIX / PHOBOS /BRAHMS 17.4 GeV SPS : NA44, WA97 from this meeting statistical error only statistical error only Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

7. Net-proton • Inclusive net-proton • Net-proton increases with centrality Measured in STAR acceptance Extrapolated yields BRAHMS preliminary STAR data : from this meeting BRAHMS data : Quark Matter 2001 Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

8. Chemical freeze-out model Refs. J.Rafelski PLB(1991)333 J.Sollfrank et al. PRC59(1999)1637 Hadron resonance ideal gas Particle density of each particle Qi : 1 for u and d, -1 for u and d si : 1 for s, -1 for s gi:spin-isospin freedom mi : particle mass Tch : Chemical freeze-out temperature mq : light-quark chemical potential ms : strangeness chemical potential gs : strangeness saturation factor All resonances and unstable particles are decayed Comparable particle ratios to experimental data Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

9. Chemical fit result Central K+/K- • Chemical freeze-out • parameters • Tch = 179±4 MeV • mB = 51±4 MeV • ms = -0.8±2.0 MeV • gs = 0.99 ±0.03 • c2/dof = 1.5 BRAHMS PHENIX PHOBOS STAR X+/X- p-/p+ p/p L/L K+/p+ K-/p- p/p+ K+/h- Ratio (chemical fit) K-/h- p/p- K0s/h- K*0/h- L/h- L/h- f/h- X-/h- X+/h- Model: M.Kaneta, Thermal Fest (BNL, Jul 2001), N.Xu and M.Kaneta, nucl-ex/0104021 Ratio (data) Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

10. Chemical freeze-out Lattice QCD predictions central collisions • Beam energy dependence • Temperature increases • Baryon chemical potential decreases • At RHIC • Being close to phase boundary • Fully strangeness equilibration (gs~1) RHIC 130GeV SPS Baryon Chemical Potential mB [GeV] Neutron star parton-hadron phase boundary <E>/<N>~1GeV, J.Cleymans and K.Redlich, PRC60 (1999) 054908 Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

11. Identified single particle spectra s • Transverse momentum distributions • Boltzmann-like distribution • Information of thermal (kinetic) freeze-out • Temperature • Radial flow • The pressure gradient generates collective motion Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

12. mT distribution at RHIC 0.8 0.6 0.6 0.5 0.4 0.4 0.6 p- centrality p X+, X- L K+ K- STAR Preliminary K0s Central events (top 14%) dE/dx 0.2 < pT < 2.4 0.4 < pT < 3.6 K- K+ f K*0 Statistical error only p kink method MT-M0 (GeV/c2) Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

13. Slope parameter vs. centrality and mass L L from Quark Matter 2001 • Inverse slope parameter • Increasing • with centrality • with particle mass p p K K p p from J. Burward-Hoy’s talk in Thermal fest (BNL, Jul 2001) from H.Long’s talk this meeting K0s Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

14. Radial flow and temperature p  from J. Burward-Hoy’s talk in Thermal fest (2001 Jul.) PHENIX Preliminary • Spectra are describe by Tth and < r > • Also, hydrodynamical model can reproduce the data Tth = 120+50-25 [MeV] <br>= 0.52+0.12-0.08 [c] solid : used for fit - c2 /dof = 30.4/35 K- Tth ~ 104  21 [MeV] < r > ~ 0.5  0.1 [c] fit by M.Kaneta to STAR Preliminary data The model is from E.Schenedermann et al. PRC48 (1993) 2462 based on Blast wave model Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

15. Tth and <br> systematic <r> [c] Tth [GeV] STAR PHENIX • <r> • saturates around AGS energy • increased at RHIC? • Tth • saturates around AGS energy • behavior in (1-10 GeV) predicted by Stocker et al. in 1981 and Hagedorn • Need 200GeV data and lower energy data Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

16. Event anisotropy z Masashi Kaneta y x • The pressure gradient generates collective motion (aka flow) • Central collisions • radial flow • Peripheral collisions • radial flow and • anisotropic flow Almond shape overlap region in coordinate space Momentum space Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

17. v2 vs. centrality at RHIC Charged hadron mid-rapidity: |h |<1.0 Hydrodynamic limit STAR: PRL86 (2001) 402 PHOBOS preliminary (PHOBOS : Normalized Paddle Signal) • Central region follows Hydrodynamical model at RHIC Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

18. v2 of identified particle Hydrodynamical model results Event anisotropy v2 STAR PRL87 (2001)182301 pT [GeV/c] • Blast wave mode and hydrodynamical model can describe data in low pT (~2GeV/c) • Mass dependence • Typical hydrodynamic behavior  K p  STAR preliminary 0.2 from J. Fu’s talk this meeting Event anisotropy v2 0.1 STAR Preliminary from this meeting 0 2 3 1 0 pT [GeV/c] Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

19. Energy dependence of v2 RQMD(v2.4) • Elliptical flow v2 increases with collision energy min-bias charged hadron Data Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

20. Particle correlation (HBT) • Probe of the space time extent of heavy ion collisions • Radius parameters • space-time geometry of the emitting source • dynamical information (e.g. collective flow) Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

21. Radius parameters pp correlation • similar radius with SPS! • strong space-momentum correlation? Kt = pair Pt Rside Rout STAR data : PRL87(2001) 082301 Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

22. Radii vs. pT STAR PRL87(2001) 082301 Blast wave model : Mike Lisa, ACS Chicago, 2001 PHENIX Preliminary from this meeting • However • Hydrodynamical QGP + (uRQMD or RQMD) can not reproduce Ro<Rs PRL86 (2001) 3981 S. Soff, S.A. Bass and A. Dumitru • Blast wave model describes pT dependence • Consistent Tthand br with them from spectra and v2 p+p+ p-p- model: R=13.5 fm, t=1.5 fm/c Tth=0.11 GeV, br = 0.5 c pT [GeV/c] Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

23. Summary (I) • Many new interesting results from RHIC year 1 • Not yet baryon free (p/p<1) • Chemical freeze-out • Tch~180 MeV, mB~50 MeV, ms~0 MeV, gs~1 (central) • Full strangeness equilibration! • Close to phase boundary! • Thermal freeze-out • Consistent results from spectra, HBT, and v2 • Tth~100-140MeV, <br>~0.5 • Larger flow than one at SPS • Success of hydrodynamical approach • mT spectra, v2 ,and HBT (but only by blast wave model) Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

24. Summary (II) • All hadrons are at same thermal freeze-out? • p, K, p, and L • Seem to have common Tth and radial flow • Inverse slope parameters increase with mass • However… • Cascade (X) seems to freeze-out early • Multi strange particle is one of keys for information of early stage STAR preliminary PHENIX preliminary SPS Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS

25. Open issues • What stage is the origin of strong flow? • Partonic and/or hadronic level? • We don’t have a perfect microscopic model to describe data! • Thermal/statistical model assumes ideal gas • The source may not be ideal gas in real world • How to connect from hadron observable to parton level? Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS