Yoctosecond metrology through HBT correlations from a quark-gluon plasma

TL;DR

This paper proposes using HBT intensity interferometry of direct photons to measure the extremely rapid expansion dynamics of quark-gluon plasma at the yoctosecond timescale, potentially revealing isotropization time and photon double pulses.

Contribution

It introduces a novel method to access yoctosecond scale dynamics of QGP through HBT correlations of direct photons in heavy ion collisions.

Findings

HBT correlations are sensitive to early QGP anisotropies.

Modification of HBT signals can measure plasma isotropization time.

Potential detection of photon double pulses at yoctosecond timescale.

Abstract

Expansion dynamics at the yoctosecond timescale affect the evolution of the quark gluon plasma (QGP) created in heavy ion collisions. We show how these dynamics are accessible through Hanbury Brown and Twiss (HBT) intensity interferometry of direct photons emitted from the interior of the QGP. A detector placed close to the beam axis is particularly sensitive to early polar momentum anisotropies of the QGP. Observing a modification of the HBT signal at the proposed FoCal detector of the LHC ALICE experiment would allow to measure the isotropization time of the plasma and could provide first experimental evidence for photon double pulses at the yoctosecond timescale.