Top Jets in the Peak Region: Factorization Analysis with NLL Resummation

TL;DR

This paper analyzes top-quark production at high energies in e+e- collisions, focusing on how soft radiation affects mass measurements and providing resummed predictions for invariant mass and thrust distributions.

Contribution

It develops a factorization framework with NLL resummation to accurately predict top-quark mass spectra and soft radiation effects in high-energy e+e- collisions.

Findings

Mass peak shifts by order Q LambdaQCD/m due to soft radiation treatment.

Resummed cross-section results at NLL order for peak and tail regions.

Predictions for thrust distribution of massive jets at NLL order.

Abstract

We consider top-quarks produced at large energy in e+e- collisions, and address the question of what top-mass can be measured from reconstruction. The production process is characterized by well separated scales: the center-of-mass energy, Q, the top mass, m, the top decay width, Gamma_t, and also LambdaQCD; scales which can be disentangled with effective theory methods. In particular we show how the mass measurement depends on the way in which soft radiation is treated, and that this can shift the mass peak by an amount of order Q LambdaQCD/m. We sum large logs for Q >> m >> Gamma_t > LambdaQCD and demonstrate that the renormalization group ties together the jet and soft interactions below the scale m. Necessary conditions for the invariant mass spectrum to be protected from large logs are formulated. Results for the cross-section are presented at next-to-leading order with next-to-leading-log resummation, for invariant masses in the peak region and the tail region. Using our results we also predict the thrust distribution for massive quark jets at NLL order for large thrust. We demonstrate that soft radiation can be precisely controlled using data on massless jet production, and that in principle, a short distance mass parameter can be measured using jets with precision better than LambdaQCD.