Electroweak Sudakov form factors and nonfactorizable soft QED effects at NLC energies

TL;DR

This paper analyzes the infrared behavior of electroweak corrections at TeV energies, revealing that soft QED effects do not factorize at NLC energies, which impacts how these corrections should be computed.

Contribution

It introduces a formalism to calculate leading log electroweak effects at any order, highlighting the nonfactorizable nature of soft QED effects at TeV scales.

Findings

Soft QED effects do not factorize at NLC energies.

Nonfactorizable effects appear at the two-loop LL level.

Explicit calculation for a Z' decay into fermions.

Abstract

We study the leading log infrared behavior of electroweak corrections at TeV scale energies, that will be reached by next generation of linear colliders (NLC). We show that, contrary to what happens at typical LEP energies, it is not anymore possible to disentangle ``pure electroweak'' from ``photonic'' corrections. This means that soft QED effects do not factorize and therefore cannot be treated in the usual ``naive'' way they were accounted for in the LEP-era. The nonfactorizable effects come up first at the two loop LL level, that we calculate explicitly for a fermion source that is neutral under the SU(2)$\otimes$U(1) gauge group (explicitly, a Z' decay into two fermions). The basic formalism we set up can be used to calculate LL effects at any order of perturbation theory. The results of this paper might be important for future calculations of electroweak corrections at NLC energies.