The hard bremsstrahlung correction to e^+ e^- -> 4f with finite fermion masses: results for e^+ e^- -> u d-bar mu^- nu

TL;DR

This paper introduces an improved method for calculating the hard bremsstrahlung correction in e^+ e^- collisions producing four fermions, accounting for finite fermion masses, enabling precise cross section calculations without angular cuts, crucial for background analysis.

Contribution

It presents a novel, efficient approach to include finite fermion masses in bremsstrahlung corrections, allowing phase space integrations to the collinear limit and improving accuracy in cross section predictions.

Findings

Calculated total and differential cross sections for specific e^+ e^- processes.

Demonstrated the significance of mass effects by comparing different final states.

Showed the method's applicability to background studies and gauge coupling bounds.

Abstract

An improved efficient method of calculating the hard bremsstrahlung correction to e^+ e^- -> 4f for non-zero fermion masses is presented. The non-vanishing fermion masses allow us to perform the phase space integrations to the very collinear limit. We therefore can calculate cross sections independent of angular cuts. Such calculations are important for background studies. Results are presented for the total and some differential cross sections for e^+ e^- -> u d-bar mu^- nu and the corresponding hard bremsstrahlung process. The latter is of particular interest for a detailed investigation of the effects of final state radiation. In principle, the process e^+ e^- -> u d-bar mu^- nu gamma is also interesting since it helps to set bounds on possible anomalous triple and quartic gauge boson couplings involving photons. The size of mass effects is illustrated by comparing the final states u d-bar mu^- nu (gamma), c s-bar mu^- nu (gamma) and u d-bar tau^- nu(gamma).