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Hadronization by Coalescence

Partonic Coalescence at RHIC. V. Greco , Texas A&M University, Cyclotron Institute (INFN fellow) C. M. Ko and P. Levai (KFKI). Hadronization by Coalescence. Hadron spectra ( solving proton puzzle ) Elliptic flow ( solving baryon/meson systematic,

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Hadronization by Coalescence

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  1. Partonic Coalescence at RHIC V. Greco, Texas A&M University, Cyclotron Institute (INFN fellow) C. M. Ko and P. Levai (KFKI) • Hadronization byCoalescence • Hadron spectra (solving proton puzzle) • Elliptic flow (solving baryon/meson systematic, opacity puzzle) 25-28 June, Montreal 2003

  2. Hadrons at RHIC pions protons PHENIX,nucl-ex/0212014 • Fragmentation p/p ~ 0.1 • Jet quenching should affect both PHENIX, nucl-ex/0304022 Fragmentation is not the dominant mechanism of hadronization at pT ~ 1-5 GeV !? p0 suppression: evidence of jet quenching before fragmentation

  3. Jet Fragmentation A p, K, p ... a c B b d ph= zpc, z<1 energy needed to create quarks from vacuum A,B= p, n (e+, e-) a,b,c,d= g,u,d,s…. Parton distribution after pp collision p/p < 0.2 B.A. Kniehl et al., NPB 582 (00) 514 (+ phenomenological kT smearing due to vacuum radiation)

  4. Jet Quenching Large radiative energy loss in a QGP medium GLV model, PLB538 (02)282 L/l opacity P. Levai et al., NPA698(02)631 Non – abelian energy loss weak pT dependence of quenching

  5. Coalescence vs. Fragmentation Fragmentation: • Leading parton pT ph= z pT according toa probability Dh(z) • z < 1, energy needed to create quarks • from vacuum Coalescence: • partons are already there • ph= n pT ,, n = 2,3 • to be close in phase space $ Even if eventually Fragm. takes over …

  6. Coalescence Formula fqinvariant parton distribution functionthermal (mq=0.3 GeV, ms=0.47 GeV) + quenched minijets (L/l=3.5) P. Levai et al., NPA698(02)631 fHhadron Wigner function Dx , Dp coalescence radii In the rest frame

  7. Montecarlo Method We introduce a large number of test partons with uniform momentum distribution, but with an associated probability Same statistics even if dN/d2pT go down by 10-8 T=170 MeV V ~ 900 fm-3 T ~ 170 MeV b(r)~ 0.5 r/R L/l=3.5 ET ~ 600 MeV P. Levai et al., NPA698(02)631

  8. Pion & Proton spectra Au+Au @200AGeV (central) V. Greco et al., PRL90 (03)202302 nucl-th/0305024 R. Fries et al., PRL90(03)202303 nucl-th/0306027 R. C. Hwa et al., PRC66(02)025205

  9. Hadron/Meson ratio L, X from fragm. not included! X/L ratio larger than STAR data Need of fugacity gS ~ 0.8 ?! (R. Fries et al., nucl-th/0306027) r decay

  10. Strange Hadrons spectra K- f Au+Au @200AGeV (central) For f, L, X, W fragmentation not included!

  11. Larger elliptic flow Saturation at larger pT Elliptic flow at RHIC nucl-ex/0210012 nucl-ex/0305001 Baryons than Mesons

  12. Elliptic Flow from Coalescence Possible solution to the opacity problem: D. Molnar and S.A. Voloshin, nucl-th/0302014

  13. Elliptic Flow V. G. et al., nucl-th/0305024 Light quarks v2,q from a fit to p exp. data v2,p prediction Strange quarks v2,s = 0.7 v2,q (fit to K0 exp. data) includingrdecay effect

  14. Summary & Outlook • Evidence for coalescence as dominant hadronization • mechanism at intermediate pT • Good description of spectra • Explanation of p/p , K/L ratio (coalescence hide proton quenching up to 5 GeV) • Elliptic flow of baryons & mesons • Dynamical Description • QGP & minijets partons produced at different time • Coalescence during expansion • Entropy & Energy Conservation (at low pT) • Radial & Elliptic flow self-consistently generated • Hadronic Rescattering (weak !?)

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