Abstract
Direct photons have long been considered as golden probes to study the properties of the Quark Gluon Plasma (QGP). They do not interact strongly with the medium and are produced at all stages of the collision, hence carrying information of the entire evolution of the system to the detectors. The PHENIX experiment discovered a large excess of low pT photons in Au+Au collisions at √sNN = 200 GeV compared to reference p+p collisions, which has been interpreted as thermal radiation from the QGP and hadron gas medium. At the same time, the excess photons show a large elliptic and triangular flow. These results are challenging for the current theoretical models to describe simultaneously, because on one hand the large yield suggests early stage emissions when the temperature is high, on the other hand the large anisotropy is expected to be formed only at later stages of the collision when the system has cooled off and the thermal photon production rate is expected to be smaller. Using a variety of high statistics datasets across different collision systems and energies in PHENIX, simultaneous analyses of yields and azimuthal asymmetries of direct photons with higher precision are performed to provide more constraints to the theoretical calculations. In this talk, we will present recent results on low pT direct photons measured via their external conversions to electron-positron pairs, including new results from Au+Au at lower beam energies of 39 and 62.4 GeV, as well as Cu+Cu at 200GeV.
Highlights
Photons are one of the most important probes to study the extremely dense and hot medium, Quark Gluon Plasma (QGP), created in the relativistic heavy ion collisions
We have developed a new photon reconstruction and recognition technique to analyze the conversion photons at the layers of Silicon Vertex Tracker (VTX), which will enable us to reach a better precision given the high statistics
The detector involved in the results presented in this paper is central arm of PHENIX detector, which has a π/2 azimuthal coverage in the east and west arm separately, and a -0.35 to 0.35 pseudo-rapidity coverage, as depicted in figure 1
Summary
Photons are one of the most important probes to study the extremely dense and hot medium, Quark Gluon Plasma (QGP), created in the relativistic heavy ion collisions. Unlike hadronic probes, they do not strongly interact with the medium, leaving the medium unscathed and carrying the information of its space-time creation point. PHENIX has measured the direct photon yield and anisotropy in Au+Au collisions at RHIC energies. To provide more constraints to the theoretical models and more insights into the “direct photon puzzle”, PHENIX has performed a systematic direct photon measurements across different collision systems, Au+Au and Cu+Cu, and different energies, from 39 GeV to 200 GeV. With a variety of datasets available in PHENIX, we will explore more collision systems for the future measurements
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
