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Mean Field Effect on J/psi Production in Heavy Ion Collisions

Mean Field Effect on J/psi Production in Heavy Ion Collisions. Baoyi Chen Physics Department Tsinghua University Cooperators: Kai Zhou Yunpeng Liu Pengfei Zhuang (Professor).

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Mean Field Effect on J/psi Production in Heavy Ion Collisions

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  1. Mean Field Effect on J/psi Production in Heavy Ion Collisions Baoyi Chen Physics Department Tsinghua University Cooperators: Kai Zhou Yunpeng Liu Pengfei Zhuang (Professor) Tsinghua University WeiHai July 23 2012

  2. Outline 1. Motivation 2. Transport Model & Hydrodynamics 3. Mean Field Effect on J/psi Mass 4. Numerical Results and Analysics 5. Summery Tsinghua University WeiHai July 23 2012

  3. Motivation In order to understand the properties of the QGP, weconsiderinteractions between Jpsi and the medium -----> collisions( inelastic , elastic) Inelastic collisions: nuclear absorption, gloun dissociation and regeneration Elastic collisions : mean field effect Tsinghua University WeiHai July 23 2012

  4. Motivation In order to understand the properties of the QGP, weconsiderinteractions between Jpsi and the medium -----> collisions( inelastic , elastic) Inelastic collisions: nuclear absorption, gloun dissociation and regeneration Elastic collisions : mean field effect Inelastic collisions affect Jpsi yield, pt-spectrum, v2 largely, will elastic collisions change these too? Tsinghua University WeiHai July 23 2012

  5. Motivation Mean field effect changes Jpsi mass second-order stark effect Jpsi mass shift mass shift reduces shreshold of Jpsi regeneration and makes easy regeneration -200MeV QCD sum rules (PRD 79, 011501) Tsinghua University WeiHai July 23 2012

  6. Motivation The mean field force (PRD 79, 01150) Inhomogeneous medium makes space gradients of temperature (calculated by hydrodynamics) none-zero. The attractive mean field force pulls Jpsi to the center of the fireball. and leads to a shift from high pt to low pt Tsinghua University WeiHai July 23 2012

  7. Transport Model & Hydrodynamics 1. Evolution of Medium (Energy-momentum Conservation) 2+1 demensional boost invariant + EOS with 2. J/psi Transport Equation (J/psi are so heavy, hard to be thermalied ) both inelsatic suppression regeneration elastic Tsinghua University WeiHai July 23 2012

  8. Transport Model & Hydrodynamics without elastic collisions the analytic solution is Two competition mechanism: Initial Production V.S. Regeneration with glouns、 cquark are totally thermalized Tsinghua University WeiHai July 23 2012

  9. Mean Field Effect on Jpsi Mass After considering the mass shifteffectof Jpsi, we should also consider Jpsi width. In dynamically evolutive QGP widthJ/psi decay (gloun dissociaition) mass shift mean field effect 1.J/psi width Tsinghua University WeiHai July 23 2012

  10. Mean Field Effect on J/psi Mass Qualitatively estimate J/psi width choose typical medium velocity 2 times Jpsi width increases with T, duo to higher gloun density at higher T Tsinghua University WeiHai July 23 2012

  11. Mean Field Effect on J/psi Mass Qualitatively estimate J/psi width choose typical medium velocity 2 times Jpsi width increases with T, duo to higher gloun density at higher T Jpsi width (PRD 82, 054008) Jpsi width in our model(left) is qualitatively consistent with the right figure Tsinghua University WeiHai July 23 2012

  12. Mean Field Effect on J/psi Mass assuming small elastic cross section for charmoniaat hadron level is still true at parton level. It can be solved perturbatively with (PRD 79, 01150) reduced threshold of J/psi makes regeneration more easily; the mean field force induced by inhomogeneous property of the medium pulls J/psi to the center of the fireball Tsinghua University WeiHai July 23 2012

  13. Mean Field Effect on J/psi Mass assuming small elastic cross section for charmoniaat hadron level is still true at parton level. It can be solved perturbatively The first-order solution leaving mean field force first, but keeping the temperature dependence of the mass Tsinghua University WeiHai July 23 2012

  14. Mean Field Effect on J/psi Mass assuming small elastic cross section for charmoniaat hadron level is still true at parton level. It can be solved perturbatively effective regeneration The first-order solution leaving mean field force first, but keeping the temperature dependence of the mass the second-order solution Tsinghua University WeiHai July 23 2012

  15. Mean Field Effect on J/psi Mass assuming small elastic cross section for charmoniaat hadron level is still true at parton level. It can be solved perturbatively effective regeneration The first-order solution leaving mean field force first, but keeping the temperature dependence of the mass the second-order solution The iteration converges rapidly ! Tsinghua University WeiHai July 23 2012

  16. Numerical Results and Analysics 1. Results below only expands to second-order , 2. neglecting mass shift effect on excited states of J/psi due to 3. neglecting normal suppression and shadowing effect at RHIC Tsinghua University WeiHai July 23 2012

  17. Numerical Results and Analysics reduced threshold of J/psi makes regeneration more easily + mean field force 26% ! affects regeneration only mean field force kicks J/psi to low P_t region Tsinghua University WeiHai July 23 2012

  18. Numerical Results and Analysics Due to experimental data including B-decay and shadowing effect; calculations here contains these factors too, which are absent in calculations at RHIC energies. describing exprimental data well at low pt region! ( Black lines are provided by Kai Zhou) Tsinghua University WeiHai July 23 2012

  19. Numerical Results and Analysics effective region of mean field on J/psi production is around pt=0.5GeV, which is smaller than averaged pt at RHIC and LHC: 2~3GeV So, even the mean field effect affects J/psi pt-spectra significantly, it changes total yield slightly. Tsinghua University WeiHai July 23 2012

  20. Numerical Results and Analysics 1. Global yield of J/psi is slightly enhanced by the mean field effect. Tsinghua University WeiHai July 23 2012

  21. Numerical Results and Analysics 1. total J/psi production are less affected by the mean field effect. the averaged pt square are suppressed. Tsinghua University WeiHai July 23 2012

  22. Summary 1. We developed a pertubative expansion to study the mean field effect on J/psi production. 2. Though the mean field changes global yield of J/psi slightly, it changes J/psi pt-spectrum significantly. 3. Initial J/psi production, which happens before the formation of QGP is not affected by the mean field effect; but regeneration which happens in the evolution of QGP, is largely enhancement at low transverse momentum. Tsinghua University WeiHai July 23 2012

  23. Thank you for your attention ! Tsinghua University WeiHai July 23 2012

  24. Numerical Results and Analysics Deviation exists between calculation and data at low pt, because shadowing effect, which will reduce regeneration, is not considered in this calculation. Tsinghua University WeiHai July 23 2012

  25. BUCKUP Tsinghua University WeiHai July 23 2012

  26. Tsinghua University WeiHai July 23 2012

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