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Strangeness Production and Thermal Statistical Model

Strangeness Production and Thermal Statistical Model. Huan Zhong Huang Department of Physics and Astronomy University of California, Los Angeles Department of Engineering Physics Tsinghua University. Strange Particle Discovery. 1935 Yukawa: meson exchange model for nuclear interaction

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Strangeness Production and Thermal Statistical Model

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  1. Strangeness Production and Thermal Statistical Model Huan Zhong Huang Department of Physics and Astronomy University of California, Los Angeles Department of Engineering Physics Tsinghua University

  2. Strange Particle Discovery 1935 Yukawa: meson exchange model for nuclear interaction Electromagnetic interaction – photons infinite range -- photon massless Nuclear Interaction (Strong Force) – mesons Range (Rutherford Scattering) ~ 1-2 fm Uncertainty principle DE Dt ~ hc meson mass ~ 100-200 MeV/c2 1937 Cloud Chamber  cosmic ray eventsmass 106 MeV/c2 not the Yukawa meson, muon 1947 C. Powell, C. Lattes and G. Occhialini photographic plates at a mountain top mp ~ 140 MeV/c2 pm+v

  3. Particle Discovery neutral pion p0gg 1950 accelerator experiment 1947 G.D. Rochester and C.C. Butler v – decay vertex – discovery p+ V0 p- m ~ 1000 me m+ V+ n

  4. Kaon versus pion Pions: p+p0p- Neutron pions – the anti-particle is itself !! not true to neutral K0 K0 and K0 are different particles ! u, d quark masses 5-10 MeV/c2 strange quark mass ~ 150 MeV/c2 SU(3) representation for u,d,s quarks, light quarks

  5. Strangeness Quark Mass Important!

  6. SU(3) Representation of Particles

  7. Strangeness Conservation In Strong Interaction: strange quarks can only be produced in pairs ! Associated Production: p + N  NLK+ Pair Production: p + N pNK+K- Threshold in fixed target: s = (E+mN)2 – p2 Associated Production More Effective (lower Threshold) @ low beam energies

  8. Strange Baryons Sensitive to Bulk Partonic Matter Tc~ ms

  9. The Melting of Quarks and Gluons-- Quark-Gluon Plasma -- Matter Compression: Vacuum Heating: Deconfinement High Temperature Vacuum -- high energy heavy ion collisions -- the Big Bang High Baryon Density -- low energy heavy ion collisions -- neutron starquark star

  10. High Baryon Density at the AGS Si+Si 14.6 A GeV Si+Au 14.6 A GeV Au+Au 11.7 A GeV ARC Yang Pang

  11. Systematic Kaon Measurement E802/E859/E866 Au+Au NK+ Si+Au NK+/NK- NK- NPart NPart

  12. L Measurement ~ 17 Ls per central Au+Au @ AGS

  13. Large L to p Ratio E864/E878 Anti-hyperon absorption in dense medium? Dynamical conversion of anti-protons to anti-Lambda? Similar results from E917.

  14. Strangeness is ‘enhanced’ at SPS WA97/NA57 and NA49 Consistent Results Yield N-wound No of Wounded Nucleons Baryon and anti-baryons are both enhanced, but by different amount !

  15. NPART or No Wounded Nucleons Nucleons wounded once, twice or n times are different ! NA49 Data NPart

  16. Beam-Target Fragmentation Important E910 p+A @ AGS Strange Baryon Production Increases with Number of Collisions ! NA49 results lead to the same conclusion for p+A collisions ! Both fragmentation and pair production increase @SPS !!

  17. Proton Fragmentation and Hyperon Production E941@AGS data Baryons Very Brittle! pAup+X pAun+X EQUAL

  18. Energy Dependence of Strangeness Production

  19. Mid-rapidity Ratio versus CM energy

  20. 4p Integrated Ratio versus Energy

  21. Strange Quark Production

  22. Quark to Pion Ratio Kink or Not ?

  23. @mid-rapidity Pb+Pb @SPS Many more Ws Than Ws !! The W to W Ratio

  24. Scenarios of Baryon Number Transport Direct Transport Through Gluon Junctions … W + K + K + K + (X) Indirect Transport Through Pair Production Modified by Baryon Chemical Potential … • W and W X K • X and X (L / S) K • L and L (p / n ) K Net Baryon Density Increases the Associated Production and Transfers net baryon number to multiply-strange baryons ! Event-by-Event STAR Hyperon Correlations Doable with STAR TOF and SVT Upgrade !

  25. Multi-Strange Baryon Spectrum Shape

  26. Au+Au 0-10% p+p Too Many Baryons at Intermediate pT

  27. Cannot Simply Blame Gluon Fragmentation ! (SLD) Gluon/Quark ~10-20% difference in baryon production between gluon and quark jets

  28. String Fragmentations Suppress Strange Baryons Standard string fragmentation for baryon formation through diquark tunneling out of string potential: dependence m(ud-1) = 0.49 GeV m(ud-0) = 0.42 GeV predicts S=0.35L. If S=0.35L, STAR data would imply X ~> S , very unlikely ! RQMD L 1/3 S+S-S0 Diquark fragmentation scheme for multi-strange baryon production in A+A collisions – Ruled Out ?! See M.Bleicher et al, PRL 88, 202501 (2002) on W Discussion,

  29. q q Anti-Baryon Baryon q q q q Multi-parton Dynamics and Baryon Production Baryon (Hyperon) Production may be Enhanced by Multi-parton Dynamics: Gluon Junction Mechanism -- (Kharzeev, Gyulassy and Vance ….) Junction Quark Coalescence – (ALCOR-J.Zimanyi et al, AMPT-Lin et al, Molnar+Voloshin …..) Quark Recombination – (R.J. Fries et al….) Key Measurement: S0/L Ratio  0.35 String Fragmentation  0.65-0.75 Thermal Statistical  1 Gluon Junction/Coalescence Physics Implication of multi-parton dynamics on v2 and RAA

  30. Thermal Statistical Model Particle Density Modified Bessel Function Must Include all particles including resonances !! Physical meaning of gs – phase space suppresion factor

  31. Thermal Statistical Model 200 GeV

  32. Strangeness Enhancement and gs

  33. Chemical Freeze-out @ Phase Boundary

  34. Misleadingly Appealing and Beautiful Becattini: T=170, gs=1 PBM (PLB518,(2000)41) predicts y=0 ratios almost exactly K-/K+= exp(2ms/T)(pbar/p)1/3 K- /K+=(pbar/p)1/4 is a fit to the data points Agreement Appealing ! Conceptually ? Equalibrium in local spatial region --- But Measurement in rapidity bin -- Fireball emission region in pT-y. I. Bearden, BRAHMS

  35. Kinetic and Chemical Freezeout

  36. Blast Wave where: E.Schnedermann et al, PRC48 (1993) 2462 r =s(r/R)n STAR Preliminary

  37. Blast Wave Fit Parameters: Freeze-out T; Transverse Flow Velocity bT

  38. Different Freeze-out Conditions X/W p/K/p Multi-strange Baryons freeze-out early: high T and small v Physical origin for non-zero v?

  39. Have We Observed This ?

  40. Strange Baryon Physics • Wis special – • @AGS  Quark level clustering or coalescence • @SPS  Sensitive to dynamics of baryon number transport • @RHIC  v2 and transverse radial flow reflects partonic • collectivity • There may be a special di-Omega state [W-W] ! • 2) Baryons, Strange Hyperons, -- • Multi-parton Dynamics: Gluon Junctions, Quark Coalescence • Quark Recombinations …… • We began to investigate quantitatively features which may • be related to anisotropy and hadronization properties • of bulk partonic matter ! • 3) Strange Baryons and Heavy Quarks Are Sensitive Probes of Bulk • Properties of Matter at RHIC ! • STAR’s future Barrel TOF and MicroVertex detector upgrade will • greatly enhance STAR’s physics capability on these topics.

  41. END of Talk

  42. Statistical QCD photon spin electrons spin gluon spin, color quarks spin, color, flavor Energy density reflects the information on what the matter is made of !

  43. Strange Baryons and Dynamics of Early Stages Precision Measurement of X and W Spectra Shape at the Low pT Region is Needed !! Javier Castillo

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