Nonrelativistic effective field theory of unstable top

TL;DR

This paper introduces a new nonrelativistic effective field theory for unstable top quarks, enabling precise calculations of threshold production cross sections and resolving divergence issues.

Contribution

The authors develop a novel EFT based on the decay parameter a=1-m_W/m_t, providing next-to-next-to-leading order results for top pair production.

Findings

Computed nonresonant contributions up to NNLO

Resolved divergence problems in unstable top analysis

Enhanced theoretical understanding of top quark threshold production

Abstract

We develop a new nonrelativistic effective field theory of $\rho$NRQCD [1] to describe the finite lifetime effects in the threshold production of top quark-antiquark pairs. The theory is based on the expansion in a parameter $\rho=1-m_W/m_t$ characterizing the dynamics of the top-quark decay. Within this framework we compute the nonresonant contribution to the total cross section of the top quark-antiquark threshold production in electron-positron annihilation up to the next-to-next-to-leading order. Our method naturally resolves the problem of spurious divergences in the analysis of the unstable top production.