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Heavy Ion Collisions at LHC in a Multiphase Transport Model

Heavy Ion Collisions at LHC in a Multiphase Transport Model. L.W. Chen 1 , B.A. Li 2 , Z.W. Lin 3 , B.W. Zhang 4 ,B. Zhang 5, C.M Ko 6. A multi-phase transport (AMPT) model Rapidity and transverse momentum distributions Anisotropic flows: elliptic & hexadecupole

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Heavy Ion Collisions at LHC in a Multiphase Transport Model

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  1. Heavy Ion Collisions at LHC in a Multiphase Transport Model L.W. Chen1, B.A. Li2, Z.W. Lin3, B.W. Zhang4,B. Zhang5, C.M Ko6 • A multi-phase transport (AMPT) model • Rapidity and transverse momentum distributions • Anisotropic flows: elliptic & hexadecupole • Two-pion and two–kaon interferometries • Thermal charm production • Jet flavor conversions 1Shanghai Jiao Tong Univ., 2Texas A&M Univ.-Commerce 3East Carolina Univ., 4Huazhong Normal Univ. 5Askasas State University, 6Texas A&M University Work supported by NSF and Welch Foundation

  2. A multiphase transport (AMPT) model Default: Lin, Pal, Zhang, Li & Ko, PRC 61, 067901 (00); 64, 041901 (01); 72, 064901 (05); http://www-cunuke.phys.columbia.edu/OSCAR • Initial conditions: HIJING (soft strings and hard minijets) • Parton evolution: ZPC • Hadronization: Lund string model for default AMPT • Hadronic scattering: ART String melting: PRC 65, 034904 (02); PRL 89, 152301 (02) • Convert hadrons from string fragmentation into quarks and antiquarks • Evolve quarks and antiquarks in ZPC • When partons stop interacting, combine nearest quark and antiquark to meson, and nearest three quarks to baryon (coordinate-space coalescence) • Hadron flavors are determined by quarks’ invariant mass

  3. Rapidity distributions Pb+Pb @ 5.5 TeV b< 3 mb b< 3 mb σparton=10 mb Particle multiplicity at LHC increases by a factor of ~ 4 from that at RHIC

  4. Identified hadron rapidity distributions at LHC At midrapidity, Nπ≈ 5 NK ≈ 14 Np

  5. Transverse momentum distributions 0 < b < 3 fm Particle transverse momentum spectra are stiffer at LHC than at RHIC → larger transverse flow

  6. Quark elliptic flows Au+Au @ 200 GeV Quark elliptic flows are larger at LHC than at RHIC, reaching ~ 20%

  7. Pion and Proton Elliptic flow at LHC Elliptic flow is larger for pions but smaller for protons at LHC than at RHIC

  8. Heavy meson elliptic flows at LHC Quark coalescence model

  9. Light Quark and pion hexadecupole flows at LHC naïve coalescence model AMPT model ~1.2 at RHIC

  10. Strange Quark and phi hexadecupole flows at LHC Coalescence model AMPT model ~1.2 at RHIC

  11. Deuteron elliptic flow at LHC Y. Oh & CMK • Filled circles: proton v2 from AMPT • Dotted line: fitted proton v2 • Dashed line: deuteron v2 from coalescence model including deuteron wave function effect • Solid lines: deuteron v2 from a dynamic model based on reactions NN→dπ and NNN→dN Pb+Pb @ 5.5 TeV, b=8 fm Coalescence model is a very good approximation for weakly bound particles

  12. Pion interferometry Two-pion correlation functions smaller at LHC than at RHIC

  13. Kaon interferometry Two-kaon correlation functions smaller at LHC than at RHIC

  14. Radii from Gaussian fit to correlation functions Source radii for pions are larger than for kaons and both are larger at LHC than at RHIC

  15. Emission source functions Shift in out direction - Strong correlation between out position and emission time - Large halo due to resonance (ω) decay and explosion → non-Gaussian source

  16. Thermal charm production in QGP B.W. Zhang & CMK mc=1.3 GeV • Large thermal charm production • Next-leading order and leading • order contributions are comparable • Insensitive to gluon masses • Effect reduced by about 2 for initial • temperature T0=600 MeV or for • mc=1.5 GeV

  17. Jet conversions in QGP W. Liu, B.W. Zhang & CMK • Quark jet conversion Elastic process: qg→gq Gluon is taken to have a larger momentum in the final state Inelastic process: • Gluon jet conversion: similar to above via inverse reactions

  18. Proton to π+ ratio at high transverse momenta p/πratio similar to that in p+p collisions at RHIC when quark and gluon conversion widths are multiplied by KC~4-6. It is lower than p+p at LHC.

  19. Summary Compared to RHIC, heavy ion collisions at LHC have: • ~ factor of 4 larger charged particle multiplicity • larger transverse flow • larger elliptic flow for pion and smaller one for protons • large heavy quark and meson elliptic flows • smaller v4/v22 ratios for both quarks and hadons • smaller two-pion and two-kaon correlation functions and larger source radii • enhanced thermal charm production • smaller p/pi ratio at high pT than in p+p

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