Speaker
Dr
Rupa Chatterjee
(University of Jyväskylä)
Description
Thermal emission of photons from relativistic heavy ion collisions is believed to have a very strong temperature dependence and the high p_T thermal photons are expected to provide a glimpse of the early part of the expansion history when the system is still in the plasma phase. Photons having p_T > 1 GeV/c are thus specially suitable for probing fluctuations in the initial QCD matter density distributions. We present the p_T spectra, ratio of central to-peripheral yield and elliptic flow of thermal photons from an event-by-event ideal hydrodynamic calculation with fluctuating initial conditions (IC).
We show that fluctuations in the IC enhance the production of thermal photons significantly in the range 2 < p_T < 4 GeV/c compared to a smooth initial-state-averaged profile for Au+Au (Pb+Pb) collisions at RHIC (LHC) [1,2]. The relative effect of fluctuations in the IC is found to be stronger for peripheral collisions and for lower beam energies. Thermal photon p_T spectra are studied for different values of initial formation time \tau_0 as well as for centrality dependent \tau_0 values. We show that a suitably normalized ratio of central-to-peripheral yield as a function of collision centrality and p_T can be a useful measure of the fluctuation size scale [2].
PHENIX data for direct photon elliptic flow at RHIC is found to be significantly larger than the v_2 results obtained using ideal hydrodynamics with smooth IC in the region 1 < p_T < 6 GeV/c. We show that fluctuations in the IC increase the elliptic flow for p_T > 2 GeV/c for mid-central collisions compared to the results from a smooth initial-state-averaged profile [3]. We also show that these results depend strongly on the value of the fluctuation size scale as well as on the initial and final conditions of the hydrodynamic calculation [3].
[1] R. Chatterjee, H. Holopainen, T. Renk, and K. J. Eskola, Phys. Rev. C 83, 054908 (2011); R. Chatterjee, H. Holopainen, T. Renk, and K. J. Eskola, J. Phys. G 38, 124136 (2011).
[2] R. Chatterjee, H. Holopainen, T. Renk, and K. J. Eskola, arXiv:1204.2249 [nucl-th].
[3] R. Chatterjee, H. Holopainen, T. Renk, and K. J. Eskola [in preparation].
Primary author
Dr
Rupa Chatterjee
(University of Jyväskylä)
Co-authors
Dr
Hannu Holopainen
(Frankfurt Institute for Advanced Studies)
Prof.
Kari J. Eskola
(University of Jyvaskyla)
Dr
Thorsten Renk
(University of Jyväskylä)
Peer reviewing
Paper
Paper files:
