1 / 28

Review of particle spectrum data

Review of particle spectrum data. L ijuan Ruan ( Brookhaven National Laboratory ). Outline: What have we learnt from published data bulk properties: low p T identified particle spectra jet quenching: nuclear modification factors at high p T

brandya
Download Presentation

Review of particle spectrum data

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. Review of particle spectrum data LijuanRuan (Brookhaven National Laboratory) Outline: • What have we learnt from published data • bulk properties: low pT identified particle spectra • jet quenching: nuclear modification factors at high pT • recombination/coalescence: particle production at • intermediate pT • The recent results on • blast-wave model using Tsallis-like distributions • color charge and flavor dependence of energy loss • constrain fragmentation functions at high pT • Summary and outlook • Strangeness enhancement – Rene’s talk Workshop on Critical Examination of of RHIC Paradigms

  2. Physics Goals at RHIC S. Bass • Identify and study the properties of matter with partonic • degrees of freedom(flavor, color, sound, temperature …) • Penetrating probes: parton energy loss in the medium • identified particle spectra at high pT, • heavy flavor and quarkonia • jets … • Bulk properties: energy density, collectivity and freeze out properties • identified particle spectra at low pT, v2 … Workshop on Critical Examination of of RHIC Paradigms

  3. PID Spectra – Freeze-out dynamics RHIC’s strength of measuring many particle species: K(p); resonant and multi-strangeness states Chemical freeze-out: distribution of particle species Kinetic freeze-out: momentum spectra RHIC: Nucl. Phys. A 757 (2005) Workshop on Critical Examination of of RHIC Paradigms

  4. Chemical Freeze-out s approach 1 in central Au+Au collisions: thermalization within the framework of this model. Chemical freeze out temperature ~ 160 MeV, no centrality dependence in Au+Au, close to Tcritical; baryon chemical potential B ~20 MeV STAR: Nucl. Phys. A 757 (2005) 102 Workshop on Critical Examination of of RHIC Paradigms

  5. Kinetic freeze out properties where and Blast-wave model: E.Schnedermann et al, PRC48 (1993) 2462. peripheral central STAR: Nucl. Phys. A 757 (2005) 102 • Kinetic freeze out temperature decreases from peripheral to central collisions • Velocity profile increases from peripheral to central collisions. •  and  have smaller cross sections at hadronic stage, freeze out earlier. Workshop on Critical Examination of of RHIC Paradigms

  6. Probes between chemical and kinetic freeze out Resonances: probe hadronic interactions via re-scattering of their daughter particles and regeneration Life time: 0 (1.3 fm) ++ (1.6 fm) K* (3.9 fm) (1385) (5.5 fm) (1520) (12.6 fm)  (41 fm) … (p) > () > (K) Derive the life time of hadronic stage 3-10 fm/c PRL97(2006)132301 Phys. Lett. B 612 (2005) 181 Phys. Rev. Lett. 99 (2007) 112301 Phys. Rev. C 71 (2005) 64902 Phys. Rev. Lett. 92 (2004) 92301 Workshop on Critical Examination of of RHIC Paradigms

  7. High pT: penetrating probe q q RHIC: Nucl. Phys. A 757 (2005) In central Au+Au collisions at RHIC: Fragmentation + energy loss at pT > 6 GeV/c: Significant suppression of inclusive charged hadron observed at pT>6 GeV/c: dNg/dy~1000.M. Gyulassy et al., nucl-th/0302077. Workshop on Critical Examination of of RHIC Paradigms

  8. Intermediate pT: baryon/meson pattern At pT~2 GeV/c, pbar/ ratio ~1. It can not be factorized jet fragmentation(Dq/g(pbar)/Dq/g() << 1). At 2<pT<5 GeV/c, p,  increase faster than , KS, K from peripheral to central collisions. STAR: Phys. Rev. Lett. 92 (2004) 052302; PHENIX: Phys. Rev. Lett. 91 (2003) 172301; V. Greco, et al., Phys. Rev. Lett. 90, 202302 (2003). Workshop on Critical Examination of of RHIC Paradigms

  9. hydro+jet: interplay between soft and hard Au+Au at b=2 fm soft T.Hirano & Y.Nara(’03), PRC69(2004)034908 hard Hydrodynamic afterburner Crossing pT moves toward high pT (1/pT)(dN/dpT) Jet quenching T. Hirano, QM2004 pT Interesting region Intermediate pT (2<pT<3.5 GeV/c) Pion hard,Protonsoft PT, cross~ 1.8 GeV/c for  2.7 GeV/c for K 3.7 GeV/c for p NSOFT~NHARD Workshop on Critical Examination of of RHIC Paradigms

  10. Consequence from hadron species dependent pT,cross Hydro+Jet T.Hirano & Y.Nara(’03), PRC69(2004)034908 Workshop on Critical Examination of of RHIC Paradigms

  11. Recombination/Coalescence at hadronization Fragmentation works for p+p collisions for hadrons at pT > 2 GeV/c If phase space is filled with partons, recombine/coalesce them into hadrons. (hadrons at 2 < pT < 6 GeV/c) baryon enhancement, v2 NCQ scaling. fragmenting parton: ph = z p, z<1 recombining partons: p1+p2=ph R.J. Fries, QM2004 Workshop on Critical Examination of of RHIC Paradigms

  12. Recombination/Coalescence models R.J. Fries et al., Phys. Rev. C 68, 044902 (2003). R. C. Hwa et al., Phys. Rev. C 70, 024905 (2004). V. Greco et al., Phys. Rev. Lett. 90, 202302 (2003). Recombination/Coalescence modelspredict that a scale according to the number of constituent quarks in a hadron seems to govern the particle production at intermediate pT. Workshop on Critical Examination of of RHIC Paradigms

  13. Centrality Dependence: RCP in Au+Au STAR: Nucl. Phys. A 757 (2005) 102 2<pT<6GeV/c, K*,  follow meson trend  coalescence + jet model works, however, errors on K*, , , are also big. Coalescence does not necessarily mean that baryon (meson) RCP are the same. Workshop on Critical Examination of of RHIC Paradigms

  14. From previous to now • Bulk properties (energy density, collectivity and freeze out properties): pT<2 GeV/c • Jet energy loss + fragmentation: high pT>6 GeV/c • Coalescence/recombination: intermediate pT. The recent resents on: Freeze out properties: thermal-like replaced by Tsallis-like Constrain fragmentation function: light quark and gluon FFs Jet quenching: q,Q,g Workshop on Critical Examination of of RHIC Paradigms

  15. Limitation of the Blast-wave Strong assumption on local thermal equilibrium Arbitrary choice of pT range of the spectra Flow velocity <T>=0.2 in p+p Lack of non-extensive quantities to describe the evolution from p+p to central A+A collisions in p+p collisions Levy function or mT power-law in A+A collisions Boltzmann or mT exponential pp@200GeV minbias STAR PRL99 Workshop on Critical Examination of of RHIC Paradigms 15

  16. Tsallis statistics in Blast-wave model BGBW: With Tsallis distribution: Tsallis Blast-wave (TBW) equation is: Workshop on Critical Examination of of RHIC Paradigms 16

  17. Fit results in Au+Au collisions Zebo Tang,Yichun Xu, Lijuan Ruan, Gene van Buren, Fuqiang Wang and Zhangbu Xu, Phys. Rev. C 79, 051901 (R) (2009) Workshop on Critical Examination of of RHIC Paradigms 17

  18. Fit strange hadrons only All available species Strangeness, Au+Au 0-10%: <b> = 0.464 +- 0.006 T = 0.150 +- 0.005 q = 1.000 +- 0.002 chi^2/nDof = 51/99 Tstrange>Tlight-hadrons Strangness decouple from the system earlier M. Shao, L. Yi, Z. Tang, H. Chen, C. Li and Z. Xu, arXiv:0912.0993 Workshop on Critical Examination of of RHIC Paradigms 18

  19. Centrality dependence for T and <bT> strange non-strange non-strange strange strange non-strange non-strange strange • Multi-strange hadrons decouple earlier • Hadron rescattering at hadronic phase doesn’t produce a collective radial flow, instead, it drives the system off equilibrium • Partons achieve thermal equilibrium in central collisions M. Shao, L. Yi, Z. Tang, H. Chen, C. Li and Z. Xu, arXiv:0912.0993 Workshop on Critical Examination of of RHIC Paradigms 19

  20. Flavor and color charge dependence of energy loss STAR:PRL98(2007) 192301 STAR: PRL97,152301(2006) Bottom energy loss, significantly as light flavor: no mass effect on partonic energy loss? heavy quark spectra steeper than calculated in the FONLL calculations? Collisional dissociation of heavy mesons, in-medium heavy resonance diffusion, multi-body mechanisms might play an important role for heavy quark energy loss A. Adil and I. Vitev, Phys. Lett. B649, 139 (2007); H. van Hess, V. Greco and R. Rapp, Phys. Rev. C 73; 034913 (2006); W. Liu and C. M. Ko, nucl-th/0603004 Common suppression of protons and pions: no color charge dependence of partonic energy loss? Workshop on Critical Examination of of RHIC Paradigms

  21. Discussion: g/q jets conversion in the medium • gluon/quark jets conversion in the medium. (W. Liu et al.,nucl-th/0607047; C.M. Ko, ISMD2006.) elastic scattering: q g <-> g q, qbar g <-> g qbar. inelastic scattering: q qbar<->g g • There is net quark to gluon jets conversion in the medium. • A much larger net conversion is needed to explain the data. At RHIC, initially produced hard strange quarks are much fewer than the strange quarks in a hot, dense medium. The interaction between the initially produced light quark (gluon) and the medium will lead to more strangeness production at high pT Using the same factors, Liu and Rries predicts RAA(KS0) > RAA () This leads to jet hadron chemistry change in AuAu collisions compare to in pp collisions. W. Liu and R. Fries, PRC77(2008)054902 gluon Quark Workshop on Critical Examination of of RHIC Paradigms

  22. Jet hadro-chemistry in Au+Au and p+p STAR Preliminary STAR Preliminary • The final jet hadro-chemistry change was observed: • K/ (Au+Au) > K/ (p+p); RAA(p+pbar, K) > RAA () ~ RAA() • Consistent with jet conversion mechanisms and/or modified enhanced parton splitting in the hot, dense medium S. Sapeta and U.A. Wiedemann, arXiv:0707.3494 • How significant the effect is? Yichun Xu, QM2009 Workshop on Critical Examination of of RHIC Paradigms

  23. Sample of RAA in PHENIX C. Vale QM2009 Workshop on Critical Examination of of RHIC Paradigms

  24. Constrain Fragmentation Functions: kaon in 200 GeV p+p at high pT STAR preliminary STAR preliminary Spectra in p+p collisions at pT>2 GeV/c: convolution of PDFpQCDFF Charged and neutral kaons are extended up to 15 GeV/c in p+p collisions. Charged and neutral kaons are consistent; provide constraints on FFs. Low pT KS: STAR Phys. Rev. C 75 (2007) 64901 Yichun Xu, QM2009 Workshop on Critical Examination of of RHIC Paradigms

  25. Constrain fragmentation function • In 200 GeV p+p collisions • -/+, pbar/p decrease versus pT indicating valence quark effect plays a significant role at high pT in particle production • PYTHIA can describe the ratios better but deviates from the spectra data. • NLO calculations describe spectra better but deviate from ratio STAR preliminary Yichun Xu, QM2009 This is important to understand gluon/quark contribution factors to proton, pion and kaon Workshop on Critical Examination of of RHIC Paradigms

  26. Energy dependence of particle composition STAR preliminary • In 62 and 200 GeV Au+Au collisions: • Λ/KS ratio: similar peak positions. • p(pbar)/ ratios: similar shapes at pT>2 GeV/c. Phys. Lett. B 655 (2007) 104, Phys. Rev. Lett. 97 (2006) 152301 Workshop on Critical Examination of of RHIC Paradigms

  27. Constrain intermediate pT model calculations STAR preliminary, QM2006 • There are quantitative differences between data and current models at • intermediate pT. • Hard component should be able to help constrain the reco/coalescence model • calculations. Workshop on Critical Examination of of RHIC Paradigms

  28. Summary • The identified particle spectra measurements is consistent • with the picture of a hot dense medium created at RHIC. • The recent measurements call for: • Understand particle production mechanisms in p+p, constrain • fragmentation functions. • Understanding of jet quenching in detail. • Improved intermediate pT calculations by • coalescence/recombination models. • Thanks!! Workshop on Critical Examination of of RHIC Paradigms

More Related