Intermediate pT results in STAR Camelia Mironov Kent State University 2004 RHIC & AGS Annual Users' Meeting Workshop on Strangeness and Exotica at RHIC GeV/c ? pQCD ReCo Hydro

2 Camelia Mironov 2004 AGS & RHIC Users' Meeting Collision systems … Final stateInitial state Au + Au d + Au p + p

3 Camelia Mironov 2004 AGS & RHIC Users' Meeting So far … …. Many answers to find. About … -baryons/mesons differences -identified particles correlations -particle production mechanisms

4 Camelia Mironov 2004 AGS & RHIC Users' Meeting Go into details by looking at …  More Strange particles WHY? Hopefully you refreshed your memory until this hour in the afternoon, since I’m not going to go through all the reasons now B-)

5 Camelia Mironov 2004 AGS & RHIC Users' Meeting From the STAR strange particles pool …  Mass & no. of Strange Quarks content  (dss) (MeV/c 2 )Λ(uds) (MeV/c 2 )   (sss) (MeV/c 2 ) K(us) 493.7(MeV/c 2 ) K 0 s (ds) 497.7(MeV/c 2 )  (ss) (MeV/c 2 )

6 Camelia Mironov 2004 AGS & RHIC Users' Meeting Geometry of the Collision … Reaction plane x z y Non-central collision Number of participants (N part ): number of incoming nucleons (participants) in the overlap region Number of binary collisions (N bin ): number of inelastic nucleon- nucleon collisions

7 Camelia Mironov 2004 AGS & RHIC Users' Meeting A couple of tools …  Nuclear Modification Factors R < 1 at small momenta R = 1 baseline expectation for hard processes R > 1 “Cronin” enhancements (as in pA) R < 1: Suppression

8 Camelia Mironov 2004 AGS & RHIC Users' Meeting A couple of tools …  v2 (elliptic flow) Almond shape overlap region in coordinate space Anisotropy in momentum space Interactions/ Rescattering Reaction Plane v2 sensitive to early times of system Large values of flow signatures of hydrodynamic behaviour

9 Camelia Mironov 2004 AGS & RHIC Users' Meeting Some theory models used …  Soft + Quench - soft production (hydro) at low pT, quenching of pQCD jets via gluon radiation at higher pT +baryon junctions incorporated to explain large baryon yield at intermediate pT. M. Gyulassy et. al., Phys. Rev. Lett. 86 (2001) 2537  ReCombination -assumes the recombination of two and three low pT partons to form hadrons from an exponential parton pT spectrum.  Coalescence - added assumption that thermal ‘QGP’ partons can coalesce with co- moving ‘pQCD’ partons from a mini-jet. R. J. Fries et. al., Phys. Rev. C 68 (2003) V. Greco et. al., Phys. Rev. C 68 (2003)

10 Camelia Mironov 2004 AGS & RHIC Users' Meeting More details … ReCo Models Could be … Recombination dominates out to higher p t for baryons (3 q) - hadron suppression due to parton energy loss dominates later  R AA different for mesons and baryons ?

11 Camelia Mironov 2004 AGS & RHIC Users' Meeting B/B ratios …  information about the net baryon density achieved => characterizes the environment created in collision The ratio is flat in the pT range 2-5 (GeV/c2)

12 Camelia Mironov 2004 AGS & RHIC Users' Meeting B/M ratios  /K 0 s Baryon/meson ratio “anomalous” for p T <6-7 GeV/c  increases with increasing centrality  peaks in the intermediate pT region.  turns over and appears to tend to the same value for all centralities for pT ~ 5-6 GeV/c but aparently not down to the level of pp data

13 Camelia Mironov 2004 AGS & RHIC Users' Meeting B/M ratios  comparison with models M. Gyulassy et. al., Phys. Rev. Lett. 86 (2001) 2537 R. J. Fries et. al., Phys. Rev. C 68 (2003) V. Greco et. al., Phys. Rev. C 68 (2003)

14 Camelia Mironov 2004 AGS & RHIC Users' Meeting R cp … B and M  both suppressed BUT  suppressed different AND  IT IS NOT A MASS EFFECT  M

15 Camelia Mironov 2004 AGS & RHIC Users' Meeting How about v2 … The flow pattern in v 2 (p T ) for hadrons is predicted to be simple at the quark level under p T → p T /n v 2 → v 2 / n, n = (2, 3) for (meson, baryon) ReCo models WORK !

16 Camelia Mironov 2004 AGS & RHIC Users' Meeting Let’s look at … STAR very PRELIMINARY -Only statistical errors -No feed-down corrections -Errors on proton data should be ignored

17 Camelia Mironov 2004 AGS & RHIC Users' Meeting R CP vs. R AA  Canonical suppression of strange baryons??? …. Could be …  pp IS different from peripheral AA for strange baryons.  K : R CP ~ R AA  Xi, Lambda : R CP < R AA

18 Camelia Mironov 2004 AGS & RHIC Users' Meeting Identified Strange Particles Correlations STAR PRELIMINARY anti ΛK0K0 Λ Centrality

19 Camelia Mironov 2004 AGS & RHIC Users' Meeting Identified Strange Particles Correlations Trigger: 2 GeV/c < pT < 3 GeV/c Associated: 2 GeV/c < pT < 3 GeV/c Correlation difference defined as : N same - N back trigger pairs back N N N    )49.2( 

20 Camelia Mironov 2004 AGS & RHIC Users' Meeting Still ‘Correlations’ … Trigger P T N same - N back trig: , assoc : charged hadron N same - N back Trigger P T trig: , assoc : charged hadron trig and assoc : charged hadron trig: K 0 s, assoc : charged hadron STAR PRELIMINARY Triggered particles p T bins : GeV GeV GeV For Lambda, Anti Lambda, K0 short GeV For primary charged hadrons: GeV  Λ triggered jet has more associated particles on the same side than anti Λ !

21 Camelia Mironov 2004 AGS & RHIC Users' Meeting d+Au …  Difference between identified particle nuclear modification factors also seen in d+Au collisions BUT it’s smaller( 2) at intermediate p T in AuAu collisions. STAR PRELIMINARY

22 Camelia Mironov 2004 AGS & RHIC Users' Meeting Comparison of the results … Ratio of per nucleon cross sections for p+W and p+Be collisions at √s=38.8 GeV  Small difference function of √s within errors Cronin saturation???

23 Camelia Mironov 2004 AGS & RHIC Users' Meeting So … … and it’s just the beginning!  New data at 62GeV!!!  MORE AuAu 200 data!!! !!!!! Exciting!!  Spectra from a wide range of strange and multi-strange baryons and mesons in pp, dA and AA  flow calculations for multi-strange baryons  R CP, R AA, R dA  Identified strange particles correlations