Study of Initial and Final State Effects in Ultrarelativistic Heavy Ion Collisions Using Hadronic Probes

TL;DR

This paper investigates initial and final state effects in ultrarelativistic heavy ion collisions at 200 GeV, aiming to understand quark-gluon plasma formation through hadronic probes by analyzing particle yields and nuclear modification factors.

Contribution

It provides new insights into the properties of the produced matter and initial conditions in heavy ion collisions using deuteron and gold collision data at 200 GeV.

Findings

Deuteron yields inform on the size and evolution of the emitting system.

Nuclear modification factor $R_{cp}$ helps distinguish deconfinement effects from cold nuclear matter effects.

Results suggest specific signatures consistent with quark-gluon plasma formation.

Abstract

It has been theorized that if heavy nuclei (e.g. Au, Pb) are collided at sufficiently high energies, we might be to recreate the conditions that existed in the universe a few microseconds after the Big Bang. The kinetic energy of the colliding nuclei gets converted into heat, leading to a phase transition into a new state of matter: the Quark-Gluon Plasma (QGP), in which quarks and gluons are deconfined. However, we never directly get to see the QGP because as the matter cools it recombines (hadronizes) into ordinary subatomic particles. We can only hope to infer its existence from indirect experimental signatures, after hadronization. In this dissertation we attempt to shed some light on: Properties of the final state of produced matter in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. As the hot, dense system of particles from the collision zone cools and expands, light nuclei like deuterons and anti-deuterons can be formed, with a probability proportional to the product of the phase space densities of its constituent nucleons. Thus, invariant yield of deuterons, compared to the protons and neutrons from which they coalesce, provides information about the size of the emitting system and its space-time evolution. The initial conditions that led to this. This is done by looking at the nuclear modification factor $R_{cp}$ from particle production in forward and backward directions in a ``control'' experiment using d+Au collisions at $\sqrt{s_{NN}}=200$ GeV. This can allow us to distinguish between effects that could potentially be due to deconfinement, versus effects of cold nuclear matter.