1 / 29

Mixed Hadron Ratios from STAR

Mixed Hadron Ratios from STAR. Rene Bellwied, Wayne State University, for the STAR Collaboration. PID spectra in STAR Baryon/anti-baryon ratios Mixed hadron ratios Statistical models Chemical fits Quark coalescence Sudden hadronization Dynamical models Conclusions.

ayala
Download Presentation

Mixed Hadron Ratios from STAR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mixed Hadron Ratios from STAR Rene Bellwied, Wayne State University, for the STAR Collaboration • PID spectra in STAR • Baryon/anti-baryon ratios • Mixed hadron ratios • Statistical models • Chemical fits • Quark coalescence • Sudden hadronization • Dynamical models • Conclusions

  2. p / K / p - slope parameters dE/dx-analysis with TPC dE/dx , kink, V0 analysis comparison for charged and neutral Kaons mid-rapidity y=±0.1

  3. Slope Parameters via V0 PID (y=±0.5) Preliminary pt = 0.5-3.5 GeV/c Larger pt-range than dE/dx, better characterization of flow

  4. STAR B/B Ratios Ratio approaching 1.0 as strangeness content increases STAR preliminary 0.94 ± 0.13 Ratios calculated for central events at mid-rapidity, averaged over experimental acceptance in pt.With the assumption of equal acceptance of particle and antiparticle no corrections have to be applied

  5. Energy Evolution of B/B Ratio Production of baryons through pair processes increases dramati-cally with s – still not baryon free STAR preliminary Pair-process production is larger than baryon transport (ISR) Note: 2/3 of protons from pair processes, yet pt dist. the same as antiprotons

  6. Statistical models • Braun-Munzinger et al. (hep-ph/0106066) - Follows curve for <E>/<N> = 1 GeV at freezeout - Usesphenomenologicalparameterization: J. Cleymans & K. Redlich,PRL 81 (1998) 5284

  7. T and mB according to thermal model Assumption: strangeness in complete equilibrium i.e. strangeness saturation factor gs = 1

  8. I. Increase instrange/non-strangeparticle ratios II. Maximum isreached III. Ratios decrease (Strange baryonsaffected more stronglythan strange mesons) Strangeness production Lines of constant lS where: <E>/<N> = 1 GeV Braun-Munzinger et al.hep-ph/0106066

  9. Wroblewski factor evolution dependent on T and mB dominated by Kaons Wroblewski factor PBM et al., hep-ph/0106066 total mesons baryons hidden strangeness mesons Peaks at 30 A GeV in AA collisions due to strong mB dependence

  10. Statistical model fit at 130 GeV

  11. Chemical fit result Central K+/K- • Chemical freeze-out • parameters • Tch = 179±4 MeV • mB = 51±4 MeV • ms = -0.8±2.0 MeV • gs = 0.99 ±0.03 • c2/dof = 1.5 BRAHMS PHENIX PHOBOS STAR X+/X- p-/p+ p/p L/L K+/p+ K-/p- p/p+ K+/h- Ratio (chemical fit) K-/h- p/p- K0s/h- K*0/h- L/h- L/h- f/h- X-/h- X+/h- Model: M.Kaneta, Thermal Fest (BNL, Jul 2001), N.Xu and M.Kaneta, nucl-ex/0104021 Ratio (data)

  12. K/p ratio as a function of beam energy saturation ?

  13. K/p ratio as a function of beam energy

  14. Experimental L/p 4p yields

  15. STAR Preliminary Strange Baryon production as a f(centrality) Note: spectra are not feed-down corrected L yields are from fits to Boltzmann; h- yields are power law fits Saturation ? Conclusion:Strange baryon over charged particle ratio is constant

  16. (PRELIMINARY)STAR 130 GeV14% central (L/p Implications for ratios Statistical errors only Mid-rapidity ratios (*0.2) Braun-Munzinger et al.hep-ph/0106066

  17. (PRELIMINARY)STAR 130 GeV14% central (/p Implications for ratios Statistical errors only Mid-rapidity ratios (*0.2) (PRELIMINARY)STAR 130 GeV14% central (L/p Braun-Munzinger et al.hep-ph/0106066

  18. Sensitivity to multi-strange baryons Stat. model can’t get a /p ratio above 0.09 in this phase space! D. Magestro private communication

  19. X-/K- Sensitivity to multi-strange baryons X+/p Braun-Munzinger et al.hep-ph/0105229 Thermal fit resultsin T = 174 MeV, mB = 46 MeV. Grand canonicalensemble, unlikeprevious model Statistical errors only (Preliminary) STAR 130 GeV14% central data Ratios Model gets K-/p,L/p- correct, butmisses on X ratios!!! T (MeV)

  20. Predict Predict Measure Quark-Counting Ratios (ALCOR model) Biro, Levai, Zimanyi: Phys. Lett. B347 (1995) p6 Assumption: formation of a constituent quark plasma with subsequent coalesence of the quarks into hadrons

  21. Quark-Counting Ratios from STAR data Predicted Measured Quark-counting ratios are consistent with each other Will change slightly with feeddown corrections (not included here) STAR Preliminary Statistical errors only

  22. 14% central STAR Preliminary Statistical model Statistical errors only Quark coalescence for mixed ratios As mB -> 0, sensitivity of the model to particle/antiparticle ratios is lost. Must look at ratios of dissimilar species to resolve model accuracy. 130 GeV X-/p Quark coalescence (ALCOR) Quark coalescence does better with X

  23. L/p ratio correction factors Lm = L+S0+X+W L+S0 Lm pm = p+(0.64Lm+0.52S+) = p + 0.88 (L+S0+ 0.52S+ = p+1.01 (L+S0 pm/Lm = 0.74 + 0.73 p/(L+S0 p/(L+S0= 1. pm/Lm – 1.01

  24. J. Rafelski innucl-th/9907090 4.0 Model predicts “most (anti)baryons produced will carry strangeness.” QGPSudden HadronizationModel 3.0 L / p 2.0 1.0 Sudden hadronization model (1999)

  25. 4.0 3.0 L / p 2.0 (Preliminary)STAR Data Data errors not small enough to discriminate 1.0 QGP SuddenHadronization Model Sudden hadronization model (2001) J. Rafelski inhep-ph/0111467 Large ratio at AGS (and SPS) still not understood

  26. (Preliminary)STAR 130 GeV minbias data Predicts L/L ~0.8 Stat. model 200 GeV predictions Use parameterization: (CAUTION! Really for 4p ratios) Becattini et al.PRC 64 (2001) 024901 Statistical errors only

  27. (Preliminary)STAR 200 GeV minbias data Pretty close to prediction! Stat. Model Predictions Revisited Use parameterization: (Preliminary)STAR 130 GeV Data (CAUTION! Really for 4p ratios) Becattini et al.PRC 64 (2001) 024901 Statistical errors only

  28. The models that do well with the multi-strange baryon mixed ratios are models that assume a quark phase (ALCOR and Rafelski’s models) • It seems that purely hadronic statistical models fail for the description of yield and mixed ratios of multi-strange baryons. • A transport model assuming an initial plasma phase is doing well at SPS energies (Bass and Dumitru, nucl-th/0001033) and should be tested at RHIC • The HIJING model can describe the data at the SPS with a purely hadronic scenario if the following additions are applied: • baryon junction stopping and pair production: HIJING-BB • general cascade program (GCP) for hadronic rescattering: HIJING-BB + GCP • transient fluctuating fields or color ropes: HIJING-BB + GCP + Ropes What about other models ?

  29. Statistical models do well in describing anti-baryon over baryon ratios, which yields constraints on the thermal freeze-out temperature and the baryo-chemical potential. This also allows us to determine an expansion velocity in a dynamical picture (see Helen’s talk). • They also do well for Kaon and L ratios which dominate strangeness production and seem to indicate strangeness saturation. These singly strange particles carry remnant quarks and/or valence di-quarks and are thus dependent on the baryochemical potential. • The multistrange ratios still seem to indicate strangeness enhancement and are not described by the statistical models. This indicates an additional production mechanism which should be even stronger for the Omegas. Some Conclusions

More Related