1 / 34

A simple model for higher moments of net proton distributions in Au+Au and Cu+Cu collisions

A simple model for higher moments of net proton distributions in Au+Au and Cu+Cu collisions. Chun-Bin Yang 杨纯斌 Central China Normal University cbyang@mail.ccnu.edu.cn. Based on Phys. Rev. C85 , 044905 (2012) J.Phys. G40 (2013) 075103. Outline. Motivations

garry
Download Presentation

A simple model for higher moments of net proton distributions in Au+Au and Cu+Cu collisions

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. A simple model for higher moments of net proton distributions in Au+Au and Cu+Cu collisions Chun-Bin Yang 杨纯斌 Central China Normal University cbyang@mail.ccnu.edu.cn Based on Phys. Rev. C85, 044905 (2012) J.Phys. G40 (2013) 075103

  2. Outline • Motivations • Model considerations • Net-proton distributions and their moments • Centrality dependence of the distributions • Energy dependence of model parameters • Difference between results for Au+Au and Cu+Cu • Discussions

  3. Motivations • Fluctuations of conserved quantities are sensitive indicators for the structure of the created system • Moments of the distributions related to the susceptibilities • At the critical point, susceptibilities divergent

  4. Higher order moments depend on the correlation lengthξmore stronger • They can be used to get information on the critical point in QCD diagram • In HIC, the correlation length is finite due to finite system size and rapid expansion arXiv:1006.4636

  5. STAR experimental results

  6. STAR

  7. Theoretical results from AMPT AMPT: AMulti-Phase Transport model Not sensitive to the pT cut Almost the same for net proton, net charged baryon or net baryon

  8. Model considerations • Normal nuclear effects in HIC • Nuclear stopping • Average net baryon number changes withcms energy and collision centrality • Baryon pair creation in the interactions • Diffusion of baryon number and energy • Can these effects explain the data?

  9. Properties of emission source Initial property Initial mean baryon number B baryon stopping Initial baryon number N0: random Initial proton number Np

  10. Properties of emission source • Baryon pair production from the source • Randomness? Yes! • Independent? Probably! • Energy density dependent? Yes! • Centrality dependent Yes! μ is the mean number of produced pairs

  11. Properties of emission source Isospin conservation When N1 proton, N2 antiproton, N3 neutronand N4 antineutron produced Probability for having N1 protons Similarly for antiproton

  12. Properties of emission source Net-proton Δp distribution Two parameters: μandBρ

  13. Centrality dependence of parameters • If each participant nucleon has exactly the same interactions with other nucleons • Bρ∝Np • μ ∝Np • Centrality dependent interactions • Multiple scattering • Baryon diffusion parameters depending on colliding energy

  14. 200GeV Au+Au

  15. Energy dependence of parameters • Study the moments for Au+Au collisions at different energies • We have data for the moments at 19.6,39,62.4 and 200 GeV • Use four free parameters to fit the moments • Parameterize the energy dependence of the parameters • Calculate the net-proton distributions at any energy

  16. (a) 200 GeV (b) 62.4 GeV (c) 39 GeV (d) 19.6 GeV

  17. Energy dependence of parameters

  18. Model predictions

  19. At high energy, net-proton distributions become quitesymmetric, but not of Gaussian form

  20. For Cu+Cu collisions The interaction system is smaller, and baryonpair production can be correlated fitting results show c independent of centrality

  21. Discussion and conclusion • The net-proton distributions are reproducedfrom baryon stopping and pair production • Centrality and energy dependence investigated • The distributions at different energies are predicted • Questions: • Dynamical properties of sources? • Dynamics for the parameters • How to detect novel physics from the distribution?

  22. THANKS!!!

More Related