Recent Strangeness and Exotics results from RHIC

1. Recent Strangenessand Exotics results from RHIC “Little strokes fell great oaks.” Old English Proverb

2. Some of the data L (uds)200 GeV Au+Au X (dss)200 GeV Au+Au W (sss)200 GeV Au+Au L 200 GeV p+p X 200 GeV p+p W 200 GeV d+Au X 200 GeV d+Au L 200 GeV d+Au X62 GeV Au+Au W 62 GeV Au+Au L62 GeV Au+Au 200 GeV Au+Au L*(1520) (uds) S*(1385) (uus) More Au+Au and Cu+Cu soon to come !

3. Baryon density Mid-rapidity BRAHMS PRELIMINARY mb drives the production ratios Npart < 20 or low energiesL/L ratios rising Differences appearing in p-p production

4. Collision energy dependencies STAR Preliminary Pb+Pb Au+Au STAR Preliminary • s-Baryon production is ~constant at mid-rapidity. • s-Baryon rises smoothly at mid-rapidity. What determines the overall yields?

5. Centrality dependence Redlich et al. L and X yields in AuAurelative to pp rises. Canonical suppression increases with increasing strangeness Production volume not well modelled by Npart

6. Motivation from h- PHOBOS: Phys. Rev. C70, 021902(R) (2004) There’s a correlation between dNch/dh and Npart/2 small dotted lines are: dNch/dh = npp(1-x)Npart/2 + xNbin npp= Yield in pp = 2.29 ( 1.27) x = 0.13 N.B.: SPS energy only 17 GeV If know npp can predict yield at any Npart

7. HBT and dNch/dh HBT radii ~linear as a function Npart1/3 Even better in (dNch/dh)1/3 power 1/3 gives approx. linear scale Scaling works across a large energy range nucl-ex/0505014 M.Lisa et al.

8. Strangeness and dNch/dh Look at yields relative to pp SPS and RHIC data follows same curves as a func. of dNch/dη dNch/dη- strongly correlated to the entropy of the system! Entropy alone seems to drive much of the soft physics

9. Flavor dependence of scalings PHENIX D’s Participant scaling for light quark hadrons Binary scaling for heavy flavor quark hadrons Hadrons with strange quarks are add-mixture of Npart and Nbin

10. Spectral distributions 0.13 Most Central Collisions • Temperature Tkinetic is higher for baryons with higher strange quark content for Blast-wave fits. • Spectral shapes are different. T=100 MeV T=132 MeV • p,K, p <T> 200 GeV > 62 GeV Tkin 200 GeV = 62 GeV • X, W<T> 200 GeV = 62 GeV Tkin 200 GeV > 62 GeV Tkinetic from a Blast-Wave is not same as the Temperature from a Hydro Model.

11. Nuclear modification factors √sNN=62 GeV 0-5% 40-60% 0-5% 40-60% 0-5% 40-60% √sNN=200 GeV Baryon and meson suppression sets in at different pT . 62 GeV Rcp shows less suppression. Baryon and meson suppression sets in at same quark pT. Coalesence/recombination

12. Flavor independence of Modification factor? h- - u and d dominated e - c (maybe b) dominated X – s quark dominated No apparent flavor dependence of energy loss

13. RAA of strange particles Ordering with strangeness content! s-quark K±, K0s, f and h- all scale similarly Particles with strange quarks scale differently to non-strange Phase space effects dominate out to high pT

14. Model explanation Topor Pop et al. hep-ph/0505210 HIJING/BBar + KT ~ 1 GeV Strong Colour Field qualitatively describes RAA. SCF – long range coherent fields SCF behaviour mimicked by doubling the effective string tension SCF controlsqq and qqqq production rates and gs SCF only produced in nucleus-nucleus collisions RAA≠ RCP

15. mT scaling STAR Preliminary p+p 200 GeV No complete mT scaling Au-Au Radial flow prevents scaling at low mT Seems to scale at higher mT p-p Appears to be scaling at low mT Baryon/meson splitting at higher mT – Gluon jets?

16. Strange PID correlations • 50%p/pbar • Λ • Λbar • 95% п • K0s Nch/NTrigger Au+Au 0-5% 1.0<pTAssociated<2.0 • Λ • Anti-Λ • KS0 pTTrigger Hint of split between baryons and mesons in near side yield at high pT Need more stats

17. Exotics – Pentaquarks D.S. Carman, Ohio University JLab Users meeting • “The published results on the Q+ from analysis of the g2a data cannot be reproduced in the analysis of the high statistics g10 data.” • The statistical significance in the published data is a coupling of a statistical fluctuation and the underestimate of the background in the mass region of 1.54 GeV.” Q+ K + n Clas Statement 6/30/04: “Improved analysis of this data finds that the significance of the observed peak may not be as large as indicated. We expect a definitive answer from a much larger statistics data set that is currently being analyzed.”

18. Q++ and L(1520) STAR Preliminary d-Au L(1520) Same analysis used for both plots

19. Analysis continues • If pK+ peak at 1530 MeV/c2 is real I = 1 • Must be q+. • Recent JLab null result! • Yield from STAR analysis is very small • Sensitivity of other experiments? • No signal in 200 GeV p+p (8M) and Au+Au (~10M). • What do these null observations mean? • Production dynamics or unknown data set bias? • Peak a fake?

20. Strangelet search in STAR Use the forward ZDC + SMD Strangelets have high m/z ratio Acceptance depends on charge SMD Cluster shapes different Neutron Cluster Strangelet Cluster

21. Strangelet trigger

22. The results so far.. STAR Preliminary None found. Upper limits at level of a few 10-6 to 10-7 per central Au+Au collisions are set for mass  30 GeV/c2

23. Summary • Have gathered data for a very detailed study. • Evidence that strangeness production driven by the entropy of the system created, not only by Npart. • Evidence of phase space suppression out to high pT. • Starting exporation of strangeness role in fragmentation • Little or no evidence for exotica The old “QGP” oak is starting to tremble and we’re probing its core

24. How does volume affect production? • 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 Pn/Pn’ = fn(E)/fn’(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”. When reach grand canonical limit strangeness will saturate. Not new idea pointed out by Hagedorn in 1960’s (and much discussed since)

25. p-p model calculations Can EPOS reproduce multiplicity dependence? Werner Vogelsang NLO - Nice agreement with K0s, L problematic Calculations also work for p but not protons Recent EPOS calculations seem to be working Agreement due to a very strong soft component from string fragmentation in the parton ladder formalism.

26. Predictions at higher energies • Canonical suppression increases with increasing strangeness • Canonical suppression increases with decreasing energy • σ(Npart) / Npart = ε σ(pp) ε > 1 Enhancement!

27. C to GC predicts a factor 4 - 5 larger X-enhancement at √sNN =8.8 GeV than at 17 GeV But then at √s= 8.8 GeV NA57 (D. Elia QM2004) Perhaps yields don’t have time to reach limit – hadronic system?

28. On linear scales

29. RAA of Strange Particles 0-5% 0-5% Au+Au p+p Au+Au p+p Au+Au p+p STAR Preliminary STAR Preliminary √sNN=200 GeV √sNN=200 GeV s-quarks scaled with NBin u&d-quarks scaled with Npart f scaled with N Part • s-quarks scaled with NBin • u&d-quarks scaled with Npart • scaled with N Bin Mesons (h+ + h-, K0s, f) follow similar trends. Strange baryons don’t show suppression. Rcp  Raa for strange baryons. Canonical suppression in p+p …? 0-5% STAR Preliminary STAR Preliminary s-quark Ordering with strangeness content! √sNN=200 GeV Particles with strange quarks scale differently than non-strange!

30. Lots of evidence

31. No evidence

32. How does volume affect production? • 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 Pn/Pn’ = fn(E)/fn’(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”. When reach grand canonical limit strangeness will saturate. Not new idea pointed out by Hagedorn in 1960’s (and much discussed since)

33. Predictions at higher energies • Canonical suppression increases with increasing strangeness • Canonical suppression increases with decreasing energy • σ(Npart) / Npart = ε σ(pp) ε > 1 Enhancement!

34. C to GC predicts a factor 4 - 5 larger X-enhancement at √sNN =8.8 GeV than at 17 GeV But then at √s= 8.8 GeV NA57 (D. Elia QM2004) Perhaps yields don’t have time to reach limit – hadronic system?

35. Backgrounds considered and rejected p0 gg  e+e- e+e- Same-sign e’s within the K and p bands mostly in the low mass region opening angle cut  very effective removal Associated production LK+ pp- + K+ Neither source produces a narrow peak ! D++p+p and using p as K doesn’t produce peak in relevant mass range Peak seems stable to variations in mtm cuts of daughters But still looking at other sources of background

36. Exotica – Strangelets • True ground state of baryonic matter - stable/meta-stable. • Low z/A, reduced Coulomb, no fission - No limit on size. • Can grow by absorbing neutrons - new energy source. • Strangelet with A>1017 (R>5 angstrom) will not be supported • by the surface of the earth. • Strangelets with M>2MSUN Will collapse into a black hole, • Strangelets with M<2MSUN Will be similar to neutron stars.

37. Upper Limit E886 (AGS)Adam Rusek E878 (AGS)Mike Bennett E864 (AGS)K.Barish, M.Munhoz, S.Coe, JN E864 (AGS)Z.Xu, G.V.Buren, R. Hoverstein NA52(CERN)R. Klingenberg, K.Pretzel - - - STAR (RHIC) Z=-5 Z=+5 Upper limits at level of a few 10-6 to 10-7 per central Au+Au collisions are set for mass  30 GeV/c2

38. Multiplicity dependence HIJING can only match data with extreme parameters: kT = 4 GeV EPOS results eagerly awaited.