Speaker
Description
Heavy ion collision experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have resulted in the creation of an exotic state of matter: the quark-gluon plasma (QGP). Over the past two decades, our understanding of the QGP has evolved significantly, from measurements of nuclear modification functions of jets due to energy loss in medium to the realization of the applicability of hydrodynamics in matching the soft particle spectra. Direct photons exclude those from hadronic decays, and have proven themselves as versatile probes of the QGP. They are emitted at all stages of the evolution and can be soft but penetrating probes of the medium due to their electromagnetic nature and lack of final state interactions [1]. An important channel of photon production in jet-medium interactions is the conversion process, where a high energy quark or anti-quark is converted to a photon via a soft exchange with the medium [2]. In this talk, we present a new and modern calculation of direct photons created by the interaction of hard partons with the viscous relativistic fluid-dynamical medium. We calculate the conversion photon contribution to the total photon spectrum as well as to the photon $v_2$. We find that in the mini-jet domain of transverse momenta ($4 − 10$ GeV), jet- medium photons can contribute as much as 20% of the total photon yield with a significant portion coming from the conversion mechanism. We also explore the potential of conversion photons as a probe of different energy loss approaches. We perform this comparison using the conversion photon spectrum from the evolving parton distributions computed with the AMY-McGill[3] and CUJET[4,5] parton energy loss formalisms.
[1] C. Gale et al., arXiv: 2106.11216
[2] G.-Y. Qin et al., Phys. Rev. C 80 (2009) 054909
[3] B. Schenke et al., Phys.Rev.C 79 (2009) 054908
[4] M. Gyulasy et al., Nucl.Phys.B 571 (2000) 197-233
[5] S. Shi et al. Chin.Phys.C 43 (2019) 4, 044101
