1. STAR STRANGENESS! K0sK0s    K+K+ (Preliminary)         

2. What do we measure? K + (us) 494MeV  + +  c  cm K 0 s (ds) 498MeV  +  + c  cm  uds) 1116MeV p+  - c  cm   (dss) 1321MeV  +  - c  cm   (sss) 1672MeV  +K - c  cm  0 (ss) 1020MeV K + +K + c  cm + anti-particles + other more exotic resonances (  (1520)!)

3. What do we measure (2)? Particle yields How much is created? Spectra (dN/dy, dN/dp t, d 2 N/dydp t ) Where and when are they created and what are the dynamics? Particle ratios What are the chemical potentials? Interferometry How large is the source and how long did it exist?

4. T fireball < T c  Hadron gas Hard to make S  0 particles  + N   + K (E thresh  530MeV)  + K   +  (E thresh  1420MeV) Mtm phase space suppressed Need to create 3 qq pairs (initially there are no q) with similar momenta in a region already containing many quarks. Why are we interested in Strangeness production? T fireball >T c  QGP Easy to make s quarks E=2m s (  300MeV) Free gluons g-g fusion - dominate s s creation faster reaction time than qq Pauli blocking may aid creation of s s quarks ( probably not true at high T, too many states). ¯ ¯ ¯ ¯ ¯ ¯

5. What is the best thing to measure? While K’s carry ~70% of the strangeness they are easily produced in the final stage reactions as the hadrons in the expanding gas interact and already show an enhancement over N-N collisions at energies too low to form a QGP.  Want to look at the yields of multi-strange (anti-)baryons  production suppressed in Hadron Gas because a) need large energy to create b) need to create u d s where there are already many ud c) need to create them in the same mtm phase space Looking at the particle ratios  p  tells you the s/u ratio -> 1 if there is chemical equilibration ¯ ¯¯¯ ¯ ¯ ¯¯

6. Evidence for Strangeness Enhancement - WA97 results

7. Strange particle ratios AGS > 1 and is higher than SPS. Seems to be a clear strangeness enhancement between pA and AA collisions at the SPS

8. Where are the strange particles produced? If heavy ion collisions were just N-N reaction superpositions  (uds) concentrated in the baryon rich projectile regions  (uds), K 0 s (ds) peaked at mid-rapidity due to their sea-quark content PROBLEM! What if there is any stopping? Baryon-rich projectile and baryon-free “fire-ball” region become merged Have to separate fire-ball creation from that merely due to associated production

9. Stopping and the net  distribution We expect that the net  yield should follow the net p yield. However there is a distinct “bump” about mid-rapidity in the  distribution that is not observed in the p. Is this NEW physics? Or is it evidence of feed-down into the  channel that has yet to be corrected properly. NA49 have recently obtained  and  results which may help answer this question

10. Freeze out “Temperature” vs Mass From two particle correlation studies you can extract  2 /T from R . ~50% transverse kinetic energy goes into radial flow. -> Very important for any global thermo-chemical analysis T prop = 120 ±10MeV  = 0.5 N.B  (Na49) T=305 MeV  (Na50) T=213 MeV Also 3x smaller yield

13. K +/-  +/- +  K +, K - High P t identification via “Kink”Analysis

14. Finding V0s

15. STAR TPC Acceptance for B=0.25T (Half Field )

16.   — The peaks in their glory 332K Events |z|<50cm, |y|=0.5, GeV/c 0.16/event 0.13/event

17. 154K MinBias Events |z|<50cm, |y|=0.5, GeV/c And there’s more 0.0009/event0.2/event

18. STAR STRANGENESS! K0sK0s    K+K+ (Preliminary)         

19. In case you thought it was easy… Before

20. And Voila!!!! After

21. Large peaks at 2 o’clock and 8 o’clock TPC pad row “floating” Fine way to calibrate a detector.. Now in ExB “Hell”

22. Baryons distributions carry information related to –stopping and particle production –baryon chemical potential –thermal equilibrium p/p ratio should be sensitive Last call for RHIC predictions (nucl-th/9907090) at  s NN = 200 GeV : –Quark Coalescence:  p/p = 0.6 –Fireball:  p/p = 0.9 - 1.0 –Hijing:  p/p = 0.8 –RQMD:  p/p = 0.5 

23.  p/p: centrality and p t dependence No strong p t dependence Weak centrality dependence more stopping and/or other process ? 85%  centrality  6% Ratio for 0.3 < |y| < 0.4

24.  /  preliminary  = 4 MeV 332K min bias Events 0 < p t < 2.3 GeV/c 0.5<y<0.5 ¯

25. p/p  @AGS @SPS p/ p E866 + + p/ p NA49  WA97 p/ p STAR  STAR - - - - - AGSSPS RHIC STAR Preliminary  /  ratio Anti-Baryon/Baryon Ratio Preliminary:  /  = 0.70  0.05 (stat)  0.2 (syst) p/p = 0.65  0.03 (stat.)  0.06 (sys.) ¯

26. Conclusion Stay tuned for QM2001!!!!