### Speaker

Rupa Chatterjee

### Description

Thermal photon $v_3$ is calculated for 0--40% central collisions of Pb nuclei at LHC from event-by-event ideal hydrodynamic model [1]. The differential triangular flow parameter $v_3(p_T)$ calculated with respect to the participant plane (PP) is found to be non-zero, positive, and shows similar qualitative nature to the elliptic flow parameter $v_2(p_T)$ [2]. At $p_T=$ 1 GeV $v_3$(PP) is found to be about half of $v_2$(PP) however, for larger values of $p_T$ these two anisotropy parameters become comparable. The global geometry of the produced matter as well as the local fluctuations in the initial density distribution are responsible for this substantial value of the triangular flow parameter for thermal photons where $v_3$(PP) probes the initial state geometry in an indirect way via the generation of additional transverse flow. $v_3$ calculated with respect to the reaction plane as expected is close to zero. $v_3$(PP) strongly depends on the value of the fluctuation size parameter $\sigma$ especially in the higher $p_T$ region where, a larger $\sigma$ results in a smaller $v_3$(PP). In addition, the $v_3$(PP) is found to increase with the initial formation time of the system.
[1] R. Chatterjee, D. K. Srivastava, and T. Renk, arXiv:1401.7464.
[2] R. Chatterjee, H. Holopainen, I. Helenius, T. Renk, and K. J. Eskola, PRC88, 034901 (2013).

On behalf of collaboration: | None |
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### Primary author

Rupa Chatterjee

### Co-authors

Dinesh Srivastava
(Variable Energy Cyclotron Centre, Kolkata)
Thorsten Renk
(University of Jyväskylä)