Isolated photon cross section and resummation of the logarithms of the cone radius

TL;DR

This paper addresses the issue of logarithmic divergences in isolated photon cross sections caused by cone isolation criteria, demonstrating that resummation of these logarithms restores unitarity and improves theoretical predictions.

Contribution

The study shows that resumming logarithms of the cone radius in photon cross sections restores unitarity and proposes a refined isolation criterion for better experimental-theoretical agreement.

Findings

Resummation of logarithms restores unitarity in small cone isolation.

A new isolation criterion improves the theoretical description of experimental procedures.

Logarithmic effects are significant for accurate photon cross section calculations.

Abstract

The cone isolation criterion used in large-pt photon experiments generates logarithms of the cone radius in the theoretical cross sections. When a small radius is used, unitarity is violated as the inclusive cross section is smaller than the isolated one. We show that unitarity is restored when these logarithms are resummed. We also study a criterion which offers a more precise description of the experimental procedure : no isolation is imposed in a very small cone inside the standard one. In this case as well unitarity is violated and the resummation of logarithms is required.