Probing the time structure of the quark-gluon plasma with top quarks

TL;DR

This paper proposes using hadronically-decaying W bosons from top-antitop events as a novel probe to investigate the time evolution of the quark-gluon plasma created in high-energy nuclear collisions, exploiting a unique time delay feature.

Contribution

It introduces a new method to study the QGP's time structure by analyzing the time delay in W boson decay interactions within top-antitop events.

Findings

Identifies the time delay as a key observable for QGP evolution.

Suggests that top-quark momentum selection constrains the delay length.

Provides a potential new probe for the QGP's temporal development.

Abstract

The tiny droplets of Quark Gluon Plasma (QGP) created in high-energy nuclear collisions experience fast expansion and cooling with a lifetime of a few $\text{fm}/c$. Despite the information provided by probes such as jet quenching and quarkonium suppression, and the excellent description by hydrodynamical models, direct access to the time evolution of the system remains elusive. We point out that the study of hadronically-decaying $W$ bosons, notably in events with a top-antitop quark pair, can provide key novel insight, into the time structure of the QGP. This is because of a unique feature, namely a time delay between the moment of the collision and that when the $W$-boson decay products start interacting with the medium. Furthermore, the length of the time delay can be constrained by selecting specific reconstructed top-quark momenta.