Helen Caines Yale University 1 st Meeting of the Group on Hadronic Physics, Fermi Lab. – Oct Bulk matter properties in RHIC collisions

Helen Caines GHPM – Oct Outline T c – Critical temperature for transition to QGP T ch – Chemical freeze-out ( T ch  T c ) : inelastic scattering stops T fo – Kinetic freeze-out ( T fo  T ch ): elastic scattering stops ♦ Hadronic ratios. ♦ Resonance production. ♦ p T spectra

Helen Caines GHPM – Oct RHIC detectors designed for PID So far the RHIC experiments have published identified particle spectra for:  ,  , K , K 0 s, p, d, ,   ,  , K , K 0 s, p, d, ,  ±   0, , , , K *0 (892),  *(1385),   0, , , , K *0 (892),  *(1385),  *(1520) D 0, D, J/  ’s (+ anti-particles) D 0, D ±, J/  ’s (+ anti-particles) … V0 decay vertices K s   + +  -   p +  -   p +  +  -   +  -  +  +  +    + K - Au+Au 40% to 80% 0.2  p T  0.9 GeV/c  0 f 0 K 0 S  K *0 STAR Preliminary dE/dx in TPC Time of Flight (ToF) Electron ID via p/E in EMC Resonances in invariant mass spectra 

Helen Caines GHPM – Oct A theoretical view of the collision 1 Chemical freezeout (T ch  T c ) : inelastic scattering stops

Helen Caines GHPM – Oct What can Kaons tell us? Kaons carry large percentage of strangeness content. K - =  us K + =  su Ratio tells about baryon transport even though not a baryon. Changing rapidity slice changes chemistry

Helen Caines GHPM – Oct Models to evaluate T ch and  B Compare particle ratios to experimental data Q i : 1 for u and d, -1 for  u and  d s i : 1 for s, -1 for  s g i : spin-isospin freedom m i : particle mass T ch : Chemical freeze-out temperature  q : light-quark chemical potential  s : strangeness chemical potential  s : strangeness saturation factor Particle density of each particle: Statistical Thermal Model F. Becattini; P. Braun-Munzinger, J. Stachel, D. Magestro J.Rafelski PLB(1991)333; J.Sollfrank et al. PRC59(1999)1637 Assume: ♦ Ideal hadron resonance gas ♦ thermally and chemically equilibrated fireball at hadro- chemical freeze-out Recipe: ♦ GRAND CANONICAL ensemble to describe partition function  density of particles of species  i ♦ fixed by constraints: Volume V,, strangeness chemical potential  S, isospin ♦ input: measured particle ratios ♦ output: temperature T and baryo- chemical potential  B

Helen Caines GHPM – Oct Centrality and Energy Dependence ● , K,p ● , K,p, ,  STAR preliminary Au+Au at √s NN =200GeVand 62 GeV T LQCD ~ MeV ● , K,p ● , K,p, ,  Energy dependence but small N ch dependence… Close to chem. equilibrium ! Close to net-baryon free T ch flat with centrality

Helen Caines GHPM – Oct Rapidity Dependence Fit results Mean Upper/Lower error T ch,  s –Small sensitivity to y –Close to strangeness equilibration in central collisions over y=0-3 (y beam =6)  q,  s –Reflect baryon density with y BRAHMS Au+Au 200 GeV

Helen Caines GHPM – Oct (In)dependence of mid-rapidity yields  T, µ B, and V can all vary with energy, but in such a way as to ensure yields stay ~constant Preliminary

Helen Caines GHPM – Oct GeV Au+Au Results of Fit Strangeness Enhancement Resonance Suppression Au+Au only stable particle ratios well described STAR Preliminary 200 GeV p+p p+p particle ratios well described

Helen Caines GHPM – Oct How does volume affect production? When reach grand canonical limit strangeness will saturate. –Canonical (small system i.e. p-p): Quantum Numbers conserved exactly. Computations take into account energy to create companion to ensure conservation of strangeness. Relative yields given by ratios of phase space volumes P n /P n’ =  n (E)/  n’ (E) –Grand Canonical limit (large system i.e. central AA): Quantum Numbers conserved on average via chemical potential Just account for creation of particle itself. The rest of the system “picks up the slack”. Not new idea pointed out by Hagedorn in 1960’s (and much discussed since)

Helen Caines GHPM – Oct How can we observe this ♦ Canonical suppression increases with decreasing energy ♦ Canonical suppression increases with increasing strangeness σ(N part ) / N part = ε σ(pp) ε > 1 Enhancement!

Helen Caines GHPM – Oct SPS at √s= 17.3 & 8.8 GeV  C to GC predicts a factor larger  - enhancement at √s NN = 8.8 GeV than at 17.3 GeV Yields don’t have time to reach limit – hadronic system? Temperature assumed is incorrect? NA57 (D. Elia QM2004)

Helen Caines GHPM – Oct But does it over saturate or ONLY just reach saturation? And then at RHIC (200 GeV)...  not flat any more! ,K,p ,K,p,  STAR Preliminary Au-Au √s=200 GeV

Helen Caines GHPM – Oct R cp of strange particles R cp Baryons and mesons are different

Helen Caines GHPM – Oct R AA of strange particles Baryons with s quarks scale differently to non-strange. h-h- Phase space suppression in p+p vs jet suppression in Au+Au.

Helen Caines GHPM – Oct Is there a scaling?  The more strangeness you add the less it scales with N part. N part scaling Normalized to unity for 0-5% data

Helen Caines GHPM – Oct Is there a scaling?  The larger strangeness content scales better with N bin.  Still not perfect. Normalized to unity for 0-5% data N bin scaling  The more strangeness you add the less it scales with N part.

Helen Caines GHPM – Oct s quarks have different scaling?  How about scaling according to quark content? u, d – scale with N part – already observed. s – scale with N bin – appears better for strange particles. K 0 s – 1/2*N part + 1/2*N bin p – N part  – 2/3*N part + 1/3*N bin  – 1/3*N part + 2/3*N bin  – N bin  – N bin Pretty good! Does strangeness “see” a different correlation volume?  – N part

Helen Caines GHPM – Oct A theoretical view of the collision Chemical freezeout (T ch ) ~ 170 MeV Time between T ch and T fo 2

Helen Caines GHPM – Oct Resonance survival probability Chemical freeze- out Kinetic freeze- out measured lost  K K  K*K* K*K* K   K*K* K measured ♦ Initial yield established at chemical freeze-out ♦ Decays in fireball mean daughter tracks can rescatter destroying part of signal ♦ Rescattering also causes regeneration which partially compensates ♦ Two effects compete – Dominance depends on decay products and lifetime time Ratio to “stable” particle reveals information on behaviour and timescale between chemical and kinetic freeze-out K*K*  K

Helen Caines GHPM – Oct Resonance ratios Thermal model [1]: T = 177 MeV  B = 29 MeV UrQMD [2]  *  rescatt. > regen.  * rescatt. > regen.   rescatt. < regen.  * rescatt. < regen. [1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication [2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) M. Bleicher, private communication Need >4fm between T ch and T fo Small centrality dependence: little difference in lifetime!

Helen Caines GHPM – Oct A theoretical view of the collision 3 1 Chemical freezeout (T ch ) ~ 170 MeV Time between T ch and T fo  4fm Kinetic freeze-out (T fo  T ch ): elastic scattering stops 2

Helen Caines GHPM – Oct Shape of the m T spectrum depends on particle mass Two Parameters: T fo and  Fit range : m T – mass < 1 GeV/c 2 Hydro-dynamical model T fo ~110 MeV, = 0.8 c R  s s E.Schnedermann et al, PRC48 (1993) 2462  r =  s (r/R) n PHENIX Au-Au 200 GeV Lattice QCD: T c = 170  10 MeV T ch STAR Preliminary

Helen Caines GHPM – Oct ♦ , K, p: Common thermal freeze- out at T fo ~ 90 MeV ~ 0.60 c ♦  : Shows different thermal freeze- out behavior: T fo ~ 170 MeV ~ 0.45 c Multi-strange Kinetic Freeze-out T dec = 100 MeV Kolb and Rapp, PRC 67 (2003)  Hydro does not need different T for multi-strange  Freeze-out T different – Is blastwave realistic? Are re-interactions till freeze-out realistic either? Blastwave parameterization Higher temperature Lower transverse flow Probe earlier stage of collision?

Helen Caines GHPM – Oct p+p is not trivial

Helen Caines GHPM – Oct p T spectra vs multiplicity 1) Re-bin and Divide by min.bias 2) Scale by: /  high mult. spectra are more enhanced at high p T then K 0 s → More contribution of Minijets ??

Helen Caines GHPM – Oct Summary  Appear to have strangeness saturation at most central top RHIC energies but not before (  s = 1).  Do s quarks “ see“ a different correlation volume to light quarks?  There is a rescattering between T ch and T fo.  There is strong radial flow in Au-Au system.  Seems that  and  freeze-out differently.  62.4 GeV rather similiar to 200 GeV Our simple thermal pictures are only approximately correct. The devil is in the details but we have the data to figure it all out.

Helen Caines GHPM – Oct Backup from here

Helen Caines GHPM – Oct What happens to other particles?  – N part scaling  p – slight increase phase space suppression of baryons? K 0 s – only small phase space suppression of strange mesons? Not flat with centrality What about the  Contains  s and s quark, so not strange should show no volume dependence factor 2 increase relative to p-p

Helen Caines GHPM – Oct from BaBar

Helen Caines GHPM – Oct Scale: (N ud /N q )*N part + (N s /N q )*N bin Scale: (N ud /N q )*0.5*N part + (N s /N q )*N bin

Helen Caines GHPM – Oct C: N ~ V 2 (V  0) GC: N ~ V (V  ) Assume V ~ N part Pions/A part constant grand-canonical! Kaons/A part rising canonical! SIS energies KaoS M. Mang et al. J. Cleymans, H. Oeschler, K. Redlich, PRC 59 (1999)

Helen Caines GHPM – Oct Seems OK at SPS too Again not bad except for peripheral bin - errors large. Normalized to unity for 0-5% data

Helen Caines GHPM – Oct Thermal model reproduced data Data – Fit (s) Ratio Do resonances destroy the hypothesis? Created a Large System in Local Chemical Equilibrium Used in fit

Helen Caines GHPM – Oct Constraining the parameters

Helen Caines GHPM – Oct How about at SPS? Again :  The more strangeness the less the particle scales with N part.  N bin scaling not correct either.  u,d vs s quark scaling, not bad except for most peripheral bin - errors large. N part scaling Normalized to unity for 0-5% data N bin scaling

Helen Caines GHPM – Oct R AA of strange particles K ±, K 0 s,  and h - all scale similarlyp, ,  show hierarchy. Phase space suppression in p-p fighting jet suppression in Au-Au. h-h-

Helen Caines GHPM – Oct Flow Effect on Spectra PHENIX, STAR Preliminary 200 GeV Flow increases as centrality increases pp

Helen Caines GHPM – Oct Baryon transport to mid-rapidity Clear systematic trend with collision energy    B - all from pair production  B - pair production +  transported from y beam to y=0   B/B ratio =1 - Transparent collision   B/B ratio ~ 0 - Full stopping, little pair production ♦ ~2/3 of baryons from pair production ♦ First time pair production dominates ♦ Still some baryons from beam Preliminary

Helen Caines GHPM – Oct p-p Collective motion in Au-Au data / power law Au-Au not absolute m T scaling... but if you rescale not in Au-Au data