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The Strange Physics Occurring at RHIC

The Strange Physics Occurring at RHIC. Workshop on Strangeness and Exotica R. Bellwied, H. Caines, C.Pinkenburg, J. Velkovska RHIC & AGS Annual Users Meeting BNL May 10-14 th 2004. A theoretical view of the collision. 4. 3. 1. 2. Hadronic ratios. Resonance production.

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The Strange Physics Occurring at RHIC

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  1. The Strange Physics Occurring at RHIC Workshop on Strangeness and Exotica R. Bellwied, H. Caines, C.Pinkenburg, J. Velkovska RHIC & AGS Annual Users Meeting BNL May 10-14th 2004

  2. A theoretical view of the collision 4 3 1 2 • Hadronic ratios. • Resonance production. • pT spectra. • Partonic collectivity. High pT measurements. Tc – Critical temperature for transition to QGP Tch– Chemical freeze-out (Tch Tc) : inelastic scattering stops Tfo – Kinetic freeze-out (Tfo Tch): elastic scattering stops

  3. Baryon transport to mid-rapidity Clear systematic trend with collision energy Very similar trend between heavy ion and p-p E866 - 62.4 GeV data fits into pattern R. Witt

  4. Resonance ratios Life time [fm/c] :  = 40 L* = 13 K* = 4 Thermal model [1]: Tch = 177 MeV mB = 29 MeV NOT ENOUGH UrQMD [2] Nch [1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication [2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication Need >4fm between Tch and Tfo Small centrality dependence: little difference in lifetime! O. Barranikova

  5. Resonance Feed-down Might finally be able to answer question about S contamination of L S+ p+ +n S- p- +n Phenix Preliminary Particle mass close to pdg value •  p+ +p ? p misidentified asn C. Pinkenburg Width ~ 10MeV

  6. Measuring f through both channels PHENIX preliminary PHENIX preliminary Yield Mass (GeV/c2) Φ K+K- (min bias 200 GeV) Mass and width agree within errors with PDG values Φ e+e- (min bias 200 GeV) Yield Mass (GeV/c2) D. Mukhopadhyay

  7. Modeling the Spectra K0s upper L lower Centrality (0-5%) HIJING/BBar v2.0 right HIJING v1.37 left Need extra strings and rope breaking to obtain strange particle yields Also reasonable ratios as function of centrality V. Topor-Pop

  8. Low pT results Au+Au sNN = 200 GeV PHENIX spectra for mT < 1GeV/c2 fit with: PHENIX - open symbols PHOBOS –closed symbols -1 for mesons +1 for baryons This fit extrapolates smoothly to the low-pT points • No enhancement of low-pT particle yields Solid line = fit to PHENIX spectra Dashed line = extrapolation of fit Low pT results are vital for getting spectral shapes C. Henderson

  9. pT vs Mass STAR Preliminary ISR parameterization fails for heavy particles Same <pT> for p-p and Au-Au for heavy particles? Different <pT> with Nch, heavier particles different mult. bias R. Witt

  10. Phase space suppression less at RHIC [Tounsi & Redlich: hep-ph/0111159] STAR Preliminary 200 GeV 130 GeV See drop in “enhancement” at higher energy for W Enhancement values not as predicted by model Correlation volume not well modeled by Npart H. Oeschler

  11. Suppression of identified particles Two groups (2<pT<6GeV/c): - K0s, K, K*, f (PHENIXhave f) mesons - L, X, W baryons Mass or meson/baryon effect? L L show different behaviour to K Suppression ofK sets in at lower pT Rcp K Come together again at pT ~ 6 GeV? “standard” fragmentation? Clearly not mass dependence Higher stats. this run get W and f C. Mironov

  12. Parton coalescence and medium pT recombining partons: p1+p2+p3=ph fragmenting parton: ph = z p, z<1 Mesons • When slope exponential: coalescence wins • When slope power law: fragmentation wins recombining partons: p1+p2=ph fragmenting parton: ph = z p, z<1 Baryons • Recombination p(baryons)> p(mesons)> p(quarks) (coalescence from thermal quark distribution ...) • Pushes soft physics for baryons out to 4-5 GeV/c • Reduces effect of jet quenching Do soft and hard partons recombine or just soft+soft ? Explore correlations with leading baryons and mesons C. Nonaka

  13. v2 and coalescence model Hadronization via quark coalescence: v2 of a hadron at a given pT is the partonic v2 at pT/n scaled by the # of quarks (n). Au+Au sNN=200 GeV • Works for K0s,  &  • v2s ~ v2u,d ~ 7% D. Molnar, S.A. Voloshin Phys. Rev. Lett. 91, 092301 (2003) V. Greco, C.M. Ko, P. Levai Phys. Rev. C68, 034904 (2003) R.J. Fries, B. Muller, C. Nonaka, S.A. Bass Phys. Rev. C68, 044902 (2003) Z. Lin, C.M. Ko Phys. Rev. Lett. 89, 202302 (2002) R. Seto

  14. What about Strangeness in p-p? p-p is not necessarily the best baseline Phase space suppression of strangeness in p-p C. Mironov

  15. Pentaquarks at RHIC STAR Preliminary p-p Some possible peaks need more investigation Au-Au Minbias STAR Preliminary STAR Preliminary S. Kabana, C. Ko, L. Guo, C. Pinkenburg

  16. Summary 0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c Different physics for different scales Hydro ReCo pQCD Strange particles are useful probes for each scale All evidence suggest RHIC creates a hot and dense medium with partonic degrees of freedom. Only just beginning to understand the rich physics of RHIC. Lots more to come and much already on TAPE!

  17. Agenda STAR strangeness bulk properties – O. Barannikova STAR strangeness pp results – R. Witt Phi Production in PHENIX – D. Mukhopadhay Strangeness production in PHOBOS – C. Henderson Break Thermal Model calculations for RHIC/SPS – H. Oeschler HIJING model calculations – V.Topor-Pop Intermediate pT results in PHENIX – R. Seto Lunch Intermediate pT results in STAR – C. Mirinov Recombination model calculations – C. Nonaka Pentaquark results from JLAB – L. Guo Pentaquark results from PHENIX – C. Pinkenburg Break Pentaquark results from STAR – S. Kabana Pentaquark production – theory input – C.M. Ko Roundtable – What’s next for Strangeness – All Adjorn

  18. BACK UP

  19. Determining spin and parity K+ d Q+ p Intrinsic parity- + +? + K+ p Q+ p+ Intrinsic parity- + +? - Parity Conserved  1= (-1)DL n1n2 DL = If – Ii DL = Odd DL = Even K+ d Q+ p spin 0 1 ½(?) ½ K+ p Q+ p+ spin 0 1 ½(?) 0 DL = 0 DL = 1 DL determines the decay angular distribution Determination of spin and parity will help select between theories Correlated quark & Chiral soliton models predicts Jpc=½+ (p-wave) Quark model naïve expectation is Jpc=½− (s-wave)

  20. Interpretation of the Q+

  21. Thermal model reproduces data Data – Fit (s) Ratio Do resonances destroy the hypothesis? Used in fit Created a Large System in Local Chemical Equilibrium

  22. Experimental Evidence for Q+ Mass(nK+) GeV Currently 6 Experiments have identified a peak Spring-8 Hermes CLAS gp-> Q+K*0 ITEP nNe->K0spQ+ Saphir gp->Q+ Ks0 Diana KXe->Q+N

  23. Kinetic Freeze-out Tdec = 100 MeV Kolb and Rapp,PRC 67 (2003) 044903. X • p,K,p: Tkin decreases with centrality • X: Tkin = const., coincides with Tch ! • Large flow, lots of re-interactions, thermalization likely *A. Baran et al.; nucl-th/0305075.

  24. <pT> Systematics in p-p at 200 GeV p+p at 23 GeV Mass dependence even in p-p. Not flow!

  25. Temperature and Lifetime Centrality Dependence Blast wave fit of p,K,p (Tkin +b) + Tchem  Dt ~ 6 fm/c (see poster Olga Barannikova) Dt does not change much with centrality because slight DT reduction is compensated by slower expansion velocity b in peripheral collisions. UrQMD  Dt ~ 5-20 fm/c preliminary More resonance measurements are needed to verify the model and lifetimes G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239 Life time: K(892) = 4 fm/c L(1520) = 13 fm/c Model includes: • Temperature at chemical freeze-out • Lifetime between chemical and thermal freeze-out • By comparing two particle ratios (no regeneration) results between : T= 160 MeV =>  > 4 fm/c (lower limit !!!)  = 0 fm/c => T= 110-130 MeV (1520)/ = 0.034  0.011  0.013 K*/K- = 0.20  0.03 at 0-10% most central Au+Au

  26. Quantifying the Correlation Strength trig: L, assoc : charged hadron Nsame - Nback trig: L, assoc : charged hadron Back side trig: L, assoc : charged hadron trig and assoc : charged hadron dash lines indicate estimated flow contribution Nsame - Nback trig: K0s, assoc : charged hadron Trigger PT Trigger PT Trigger PT Same side Trigger PT Correlation difference defined as : Nsame - Nback • Suppression of  as a function of pT is slightly different from the , K0s and primaries. • Under investigation whether this is an experimental effect or whether there is indeed sensitivity to quenching or production mechanism effects

  27. What Does a RHIC Collision Look Like? A Central Au+Au Collision: Npart  sNN = 40 TeV ~ 6 mJoule Our Ears are sensitive to ~10-11 ergs = 10-18 Joule = 10-12mJoule If a RHIC Collision was converted solely into noise that‘s one HI Collisions converted into COPIOUS particle production BIG BANG!

  28. mT Scaling Au-Au p-p data data / power law In p-p Not in Au-Au

  29. Charged Particle Trends 200 GeV 130 GeV K- <pT> [GeV/c] p- dNp-/dy 200/130 ratios: Consistent with being flat: <Nch> ratio: 1.190.05 (sys) ptratio: 0.99 0.02 (sys) STAR Preliminary No increase of <pt>  loss of early information? Maximum Missing Information  thermalization? Only true for p, need detailed PID information…

  30. Hydro Calculation of v2 V2 Hydrodynamic model SPS AGS PRL 86 (2001) 402 Nch/Nmax A pressure build up -> Explosion zero for central events self quenching Elliptic flow observable sensitive to early evolution of system Collective motion + large energy density ->Hydrodynamics Assumes continuum matter with local equilibrium, “thermalization” Equal Energy Density lines P. Kolb, J. Sollfrank, and U. Heinz Large v2 is an indication of early thermalization Heavy-Ion Collisions create a system which approaches hydrodynamic limit

  31. Hadron Suppression for Identified Particles L K0s Seem to come together at ~6GeV/c - “standard” fragmentation? STAR Prelimimary Is this a mass effect or a baryon/meson effect ?

  32. Different Physics for Different Regions What do we think we know ? pQCD Hydro Fragmentation and quenching of jets What are the mechanism(s) atintermediate pT? Soft pT 0 2-3 GeV/c 6-7 GeV/c ?

  33. Baryon/Meson Ratios vs Collision Centrality L/K0s ratio 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. • Therefore pT range of baryon excess is limited to < 5-6 GeV/c. • Not yet down to level in pp data Strong baryon/meson modification in Au + Au for in L/K0s ratio as reco. predicts

  34. The STAR Detector Magnet Coils Central Trigger Barrel (CTB) ZCal Time Projection Chamber (TPC) Year 2000 Barrel EM Cal (BEMC) Silicon Vertex Tracker (SVT)Silicon Strip Detector (SSD)mVertex Detector FTPCEndcap EM CalFPD TOFp, TOFrYear 2001/2003 Year 2006+

  35. Flow of multi-strange baryons Au+Au sNN=200 GeV STAR Preliminary  68.3% CL 95.5% CL 99.7% CL • , K, p: Common thermal freeze-out at Tfo ~ 90 MeV <> ~ 0.60 c • : Shows different thermal freeze-out behavior: Tfo ~ 160 MeV <> ~ 0.45 c Higher temperature Lower transverse flow Probe earlier stage of collision? But: Already some radial flow! Tfo ~ Tch Instantaneous Freeze-out of multi-strange particles? Early Collective Motion?

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