Alladi Ramakrishnan Hall

Studying inner-working of Quark-Gluon Plasma by photon+jet measurement at RHIC

Nihar Ranjan Sahoo

Shandong University

The strongly-interacting matter at high energy density and temperature is a deconfined Quark-Gluon Plasma (QGP). The QGP filled the early universe a few microseconds after the Big Bang. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab, USA, and the Large Hadron Collider at CERN, Geneva, recreate this new form of matter using energetic collisions of heavy atomic nuclei. One of the key signatures of the QGP is jet quenching. This phenomenon arises from the interaction of a highly virtual quark or gluon with the QGP and finally fragments into a collimated spray of hadrons known as a jet. The measurement of jets recoiling from highly energetic direct photon is a valuable probe of the QGP since the direct photon does not interact in this hot-dense quantum chromodynamics (QCD) medium and provides a good reference for the recoil jet energy, against which jet modifications can be gauged. In this seminar, I will introduce the jet quenching phenomenon and its consequences. I describe how my measurement techniques in the STAR experiment at RHIC using semi-inclusive photon+jet enables us to explore the inner-working of the QGP. Recent findings on jet-medium interaction and trigger-jet acoplanarity measurements in heavy-ion collisions at RHIC will be discussed. Finally, I conclude my talk with a succinct discussion on the future measurements and their physics motivation.