1 / 22

Study the early stage of heavy ion collisions with direct photons

Study the early stage of heavy ion collisions with direct photons. Fu-Ming Liu （刘复明） Central China Normal University （ 华中师范大学）. HNP2013. 201 3 . 7 .1 8 -12 Zhangjiajie. Outline. Introduction: heavy i on c ollisions and QGP formation Puzzle:

cybil
Download Presentation

Study the early stage of heavy ion collisions with direct photons

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. Study the early stage of heavy ion collisions with direct photons Fu-Ming Liu （刘复明） Central China Normal University （华中师范大学） HNP2013 2013.7.18-12 Zhangjiajie

  2. Outline • Introduction: heavy ion collisions and QGP formation • Puzzle: the observed large elliptic flow of EM probes • Efforts to solve the large elliptic flow puzzle • Conclusions and Discussions 2

  3. Heavy Ion Collisions and QGP signals

  4. Heavy Ion Collisionsand QGP • Questions: When is QGP formed? How is QGP formed? (unperturbative) The early stage of HIC is indeed poorly known. HIC ==> QGP  HG  dilute hadrons γ dileptons Detectors EM : emitted during the “whole” evolution, called as “golden probes” of QGP, sensitive to the early stage. 4

  5. Photons and dileptons from Plasma PHENIX, Phys. Rev. Lett. 104, 132301 (2010) STAR, arXiv: 1305.5447

  6. Puzzles: Large v2 of EM probes PHENIX, Phys. Rev. Lett. 109, 122302 (2012), large v2 of direct photons v2~15% STAR, arXiv: 1305.5447, Large v2 of dileptons, As large as hadronic v2!

  7. Large v2 of direct photons at LHC! Quark Matter 2012 ArXiv: 1212.3995 7

  8. Why Large v2 of EM probes is a puzzle? Why as large as hadronic v2 is even more puzzle?

  9. Elliptic flow and triangle flow…

  10. Large v2, why puzzle Averaged initial condition Asymmetry Flow, Lorentz boost  v2 Hadrons are produced later, where flow velocity is big. Thermal photons are mostly produced earlier/inner, where flow is weak. 10

  11. Expected Ellptic flow of photons FML, T.Hirano, K.Werner, Y. Zhu, Phys.Rev.C80:034905,2009. Chatterjee et al, arXiv:1305.6443 . Observed v2 is much large than expected, by a large factor, ~ 5 ! It is difficult to explain a factor of 5 with viscosity, fluctuation,… .

  12. Suggestion 1: new photon sources • Conformal anomaly as a photon source (Basar, Kharzeev, Skokov, PRL2012) Problem: Not vanish at large pt. PHENIX, Phys. Rev. Lett. 109, 152302 (2012) 12

  13. Suggestion 2: Shuryakscenerio Shuryak, PRL (1993). Start from glue system due to PDF Prompt γ like in pp, zero v2 Quark fugacity A suppression of early emission looks helpful, but High T due to small ξ !  High emission rate at early stage. Very little help to the puzzle !

  14. Suggest a Shurak-like scenario Prompt γ like in pp, zero v2; Quark fugacity No modification of T with ξ ! Hadronic data (rapidity distribution, pt spectra and v2, …) constrain the entropy density, freeze-out T, later flow.. Take photon data to determine

  15. AuAu direct photons at RHIC Surprise: Pt spectra are not sensitive to . Large v2 implies .

  16. Pb+PbDirect photons at LHC Large v2 implies , too. Predictions:

  17. Conclusion: Shurak-like scenario Prompt γ like in pp at τ =0. Quark fugacity Bad side: Suppress early emission with ξ, but no modification of T ! Emission at glue stage via gg->qq-> g γ loop diagram? The system before is still poorly known. Good side: A natural solution for large v2 of dileptons, Glue can not couple to photons (real and virtual) directly, providing us a “dark matter” during (0, ).

  18. Thank you!

  19. Constrain system evolution (LHC) K.Werner, et al, PRC85, 064907 (2012) Hydro equation: Parameters fixed with hadron data Tau0=0.35 fm/c. Hadron data is more sensitive to freeze-out than to initialization.

  20. Constrain system evolution (RHIC) T.Hirano, et al, PRC77, 044909(2008)

  21. Pb+Pbthermal photons Begin to count thermal photons from 3-flavour QGP at tau=0.35, 0.75, …(fm/c)

  22. thermal photon v2 Flow generates with time, so does v2.

More Related