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φ -meson production and partonic collectivity at RHIC

φ -meson production and partonic collectivity at RHIC. Yu-Gang Ma Shanghai Institute of Applied Physics (SINAP), CHINA. Outline Motivation of studying φ -meson φ production and elliptic flow from RHIC Elliptic flow of φ and Ω in AMPT

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φ -meson production and partonic collectivity at RHIC

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  1. φ-meson production and partonic collectivity at RHIC Yu-Gang Ma Shanghai Institute of Applied Physics (SINAP), CHINA Outline Motivation of studying φ-meson φ production and elliptic flow from RHIC Elliptic flow of φ and Ω in AMPT φ/ Ω -trigged di-hadron correlation in AMPT Summary and conclusion Outlook Thanks to: X.Z. Cai, J.H. Chen, G.L. Ma, S. Zhang, C. Zhong, J.X. Zuo (SINAP) S. Blyth, N. Xu (LBL), J. G. Ma, H.Z. Huang (UCLA), H.B. Zhang et al. Strangeness Quark Matter (2006), UCLA, March 24-31

  2. (GeV) Flow of strange hadrons • freeze-out of strange hadrons - at higher temperature Tfo - with lower collective velocity T • small cross section of strange hadrons with non-strange hadrons • sensitivity to the early, partonic stage Strangeness Quark Matter (2006), UCLA, March 24-31

  3. Importance of  STAR: Phys. Rev. C65, 041901(R) (2002) Phys. Lett.B612, 181 (2005) •  is a true signal from the early stage of the collision! • measurements of  will conclude: • Matter status of the system at an early stage partonic vs. hadronic? • origin of observed scaling at intermediate pT mass vs. particle type? • Rescattering models (RQMD& UrQMD) which predict 2/3 phi come from kaon coalescence shows the increasing behaviors of N(phi)/N(k) and <Pt> from peripheral to central collision. • Data effectively ruled out that Kaon coalescence as a dominant channel for  production at these energies. Strangeness Quark Matter (2006), UCLA, March 24-31

  4. Production of  @ STAR Strangeness Quark Matter (2006), UCLA, March 24-31

  5. Freeze-out earlier before radial flow is completely built up? Strangeness Quark Matter (2006), UCLA, March 24-31

  6. Ratios of  to π- or K- • Phi yields increase faster than pi- in higher sqrt(Snn)  onset of strange quark degree of the freedom? • AA>pp: partonic environment favors phi production? • No strong centrality dependence of phi/K- in Au-Au collisions; • RQMD predicts increasing phi/k- vs Npart, and much smaller than the data, • Partonic interactions must play improtant role in phi production! Strangeness Quark Matter (2006), UCLA, March 24-31

  7. Discrepancy between STAR and PHENIX? STAR Preliminary X.Cai QM05, D.Pal QM05 S. Blyth, JH Chen et al. Strangeness Quark Matter (2006), UCLA, March 24-31

  8. J.Rafelski etc. PRC 72 024905 1.The integral yield from STAR is a factor of 100% higher than the PHENIX’s? 2.No! (Rafelski) Discrepancy between STAR and PHENIX?

  9. A. Kozlov m(  KK) =1.02891 ± 0.00003(stat) ± 0.00085 (syst) GeV/c2 (  KK) = 4.22 ± 0.09+0.506 MeV/c2 (  ee) = 8.9 ± 12.3 MeV/c2 dn/dy for ee tends to be larger than for KK   ee vs.  KK mass line-shapes V.Greene, QM05 Strangeness Quark Matter (2006), UCLA, March 24-31

  10. RCP and RAA STAR Preliminary by J. H. Chen & S. Blyth et al. D.Pal QM05 RCP or RAA of φ definitely follows the mesons The observed grouping behavior of RCP /RAA is a kind of meson/baryon effect but not mass effect X. Cai, QM05 S. Blyth,SQM06 Strangeness Quark Matter (2006), UCLA, March 24-31

  11. STAR Preliminary Early time information v2 vs. pT The φ experiences significant elliptic flow! Early time information: • For pT<2 GeV/c, φ flows as much as other ID'd particles, consistent with hydro. mass-ordering • For pT>2 GeV/c, φ v2 is more consistent with K0S than Λ (favors NCQ=2) • Consistent with v2 of other multi-strange hadrons (Ξ, Ω) i.e. s-quarks flow! Particle production mechanisms: • Further evidence of species-type dependence of v2 at intermediate pT (described by recombination/ coalescence models) S. Blyth, J. H. Chen et al., STAR analysis Strangeness Quark Matter (2006), UCLA, March 24-31

  12. AMPT model A Multi-Phase Transport model, Ko & Lin et al. (1) Default AMPT (2) Melt AMPT Strangeness Quark Matter (2006), UCLA, March 24-31

  13. Reconstructed φin AMPT 1.The mass width of Breit-Wigner shape has been set as 4.43MeV T.Sjostrand,arXiv:hep-ph/9508391 2.Raw-yield per (pT,φ-ψ2) has been extracted by event-mixing method 3.v2obs ~ Strangeness Quark Matter (2006), UCLA, March 24-31

  14. v2 vs pT D.Pal QM05(PHENIX) 1.Hydrodynamic behavior in AMPT (pT<1.5GeV/c), stronger v2 vs. data, 10mb partonic interaction cross section. 2.Consistent with experimental result (pT>1.5GeV/c). JH Chen& S. Blyth, STRA preliminary; AMPT: JH Chen et al., Nucl-th/0504055 Strangeness Quark Matter (2006), UCLA, March 24-31

  15. Centrality dependence of v2 Re-scattering effect in AMPT 1.Hardon-cascade can be turn on/off to investigate the re-scattering effect. 2.Re-scattering effect is small: the pressure becomes more isotropic in later hadronic matter. φ interacts weaker in the hadronic matter. Significant v2 has been observed in different centralities Strangeness Quark Matter (2006), UCLA, March 24-31

  16. ABOUT OMEGA V2 in AMPT RQMD: Y. Lu et al., nucl-th/0602009 1.NCQ scaling looks work even for Omega within error bar. stronger v2 of strange quark: phi & omega. 2. Larger v2 reveals in comparison with AMPT default and RQMD case. Partonic effect needs to produce the large v2 as the data! J. Zuo et al., preliminary AMPT results Strangeness Quark Matter (2006), UCLA, March 24-31

  17. Soft Associated particles on Away side (thermalization) <pT> from away jets near side SOFTENED BROADENED <pT> from medium decay thermalization??? away side BROADENED SOFTENED What happens to a hard probe that traverses a colored medium? soften + broaden =?= thermalization Strangeness Quark Matter (2006), UCLA, March 24-31

  18.  correlations from AMPT (3<pTtrigger<6GeV/c , 0.15<pTassoc<3GeV/c) Au+Au @200GeV/c (0-10%) • ▲melting AMPT (with later hadron rescattering ) • ● melting AMPT (without later hadron rescattering) • (3)◆ Default AMPT (with hadron rescattering) • (4)★ Default AMPT (without hadron rescattering) • (5) ■ Star preliminary Data • 0-5% (4-6)*(0.15-4) GeV/c factor=1.58 G.L. Ma, S. Zhang, YGM et al., nucl-th/0601012 Strangeness Quark Matter (2006), UCLA, March 24-31

  19. Away side: Phi-trigged correlation narrower than any-hadron trigged correlation  consistent with the scenario of earlier freeze-out of phi production? A good probe to explore strange partonic stage? Di-hadron correlation:Black: trigged by  orΩ; Blue: trigged by any hadron Preliminary AMPT results Strangeness Quark Matter (2006), UCLA, March 24-31

  20. Special identified associated particle Preliminary AMPT results Consistent with the hydro mass ordering of v2 for soft particles: Azimuthal distribution -> azimuthal correlation; Phi/omega trigged correl will be added 2 = 1/2v22 YGMa, WQShen, PRC51(1995)3256 Strangeness Quark Matter (2006), UCLA, March 24-31

  21. Nucleonic number scaling of V2 in low energy ! (Kr+Ni peripheral, IQMD) It is interesting to check p, d, t, alpha v2,v4 @ RHIC! T.Z. Yan, YGM et al, Nucleonic number scaling of V2! Strangeness Quark Matter (2006), UCLA, March 24-31

  22. Summary and conclusion • Strong suppression of high Pt power-law tail ofφ has been observed in central collisions from RHIC, the spectra can be fitted well by exponential form ( thermalization). • Observed grouping of RCP/RAA at RHIC is a kind of particle type effect but not mass effect. Strange quark DOF ~ u,d quarks • Elliptic flow of φ and Ω from AMPT with string melting scenario is consistent with the STAR-Preliminary result: φ and Ω follows NCQ scaling as other hadrons, which indicates the partonic collectivity has been formed at RHIC. Significant φv2 has been observed in different centralities. • Only hadronic stage cannot produce enough large v2-> partonic interaction is needed; Hadronic re-scattering effect on v2 ofφ is neglectble effect in AMPT model. • AMPT simulations shows that / Ω-trigged di-hadron correlations have narrow away-side Mach-cone or single peaks than all hadron-trigged Δ correlation  consistent with the earlier freeze-out of strange quarks! Experimental analysis is waiting. Strangeness Quark Matter (2006), UCLA, March 24-31

  23. outlook (1) STAR analysis: • Vector-meson (phi) spin alignment in Au+Au (global ploarized QGP?). Ideals: Recombination of q-qbar in polarized QGP; recombination of q(qbar) in polarized QGP with unpolarized qbar(q); fragmentation from polarized q(qbar) see: Liang, Wang, PRL 94(05)102301; PLB629(05)20; EXCHARM Coll, PLB 485 (00) 334 Strangeness Quark Matter (2006), UCLA, March 24-31

  24. Outlook (2) • STAR analysis: /Ω-trigged hadron correlations Narrowing of Mach-like peak or away-side peak by /Ω-trigger How about the data? Strangeness Quark Matter (2006), UCLA, March 24-31

  25. Outlook (3): Φ puzzle? With Full TOF Full TOF MRPC modules construction has been approved by NSF of China. NSFC, CAS and MoST of China will jointly support the project. It will be finished in 2.5 years. φ reconstruction with Full TOF: φ -> K+K- Φ -> e+e- Φ -> +- is there a phi puzzle in RHIC energies, esp. in lower Pt region as Model shows? S. Blyth SQM06; Z. Xu, SQM06 (TOF e, ) NA50 NA49 Open symbols: Φ -> +- Solid symbols: φ -> K+K- Pal, Ko, Lin, NPA707(02)505 Strangeness Quark Matter (2006), UCLA, March 24-31

  26. Outlook (4) K+K- azimuthal correlation (different minv) vs  v2 Low pt: • out of  Minv region: K v2>  v2  K+K- correlation >  v2 ; • inside  Minv region: K+K- correlation  phi v2 ; Middle Pt: K+K- correlation (K v2)   v2 • Is it ture in data? Strangeness Quark Matter (2006), UCLA, March 24-31

  27. Welcome to Shanghai ! Nov 16-22, 2006 Strangeness Quark Matter (2006), UCLA, March 24-31

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