Modified Coherence and the Transverse Extent of Jets

TL;DR

This paper investigates the transverse size of parton showers in jet evolution, incorporating quantum uncertainties and rescattering effects, revealing how the medium interaction diminishes with increasing parton virtuality.

Contribution

It introduces a quantum uncertainty-based approach to determine shower sizes and relates jet transport properties to gluon TMDPDF, highlighting virtuality dependence.

Findings

Transverse shower sizes are larger than classical antenna estimates.

No direct relation between shower uncertainty size and parton virtuality.

The jet transport coefficient $\

Abstract

We present a study of the transverse size of parton showers and their diminishing interaction with the medium in the high virtuality stage of jet evolution. We consider the process of a hard quark produced in deep inelastic scattering off a large nucleus. Single gluon radiation from this quark, in the absence of scattering, is re-derived using wave-packets. This allows for a derivation of the quantum uncertainty size of the hard quark, at the point of splitting. This uncertainty size is then incorporated within a Monte-Carlo shower routine yielding transverse shower sizes noticeably larger than the classical antenna size of the shower. No clear relation is found between the full uncertainty size of the shower and the virtuality of the originating parton. The single gluon emission from the hard quark is then re-analysed for the case of single rescattering off the remainder of the nucleus. A relation is derived between the jet transport coefficient $\hat{q}$ and the gluon Transverse Momentum Dependent Parton Distribution Function (gTMDPDF). Solving this relation, for a simple case, clearly demonstrates the weakening of $\hat{q}$ with the virtuality of the hard splitting parton.