Renormalization group-induced phenomena of top pairs from four-quark effective operators

TL;DR

This paper investigates how renormalization group evolution of four-quark operators influences top pair production observables, revealing new effects induced at one-loop level that are absent at tree level, with implications for phenomenology.

Contribution

It classifies RG-induced phenomena in top pair production from four-quark operators and calculates their effects, highlighting the importance of color structure in observable phenomena.

Findings

RG induces top asymmetries, polarizations, and mixings at one-loop.

Color structure determines the magnitude of RG-induced effects.

RG effects can be comparable to direct one-loop QCD and QED contributions.

Abstract

We study the renormalization group(RG) evolution of four-quark operators that contribute to the top pair production. In particular, we focus on the cases in which certain observables are \emph{first} induced from the one-loop RG while being absent at tree-level. From the operator mixing pattern, we classify all such RG-induced phenomena and underlying models that can induce them. We then calculate the full one-loop QCD RG evolution as the leading estimator of the effects and address the question of which RG-induced phenomena have largest and observable effects. The answer is related to the color structure of QCD. The studied topics include the RG-induction of top asymmetries, polarizations and polarization mixings as well as issues arising at this order. The RG-induction of top asymmetries is further compared with the generation of asymmetries from QCD and QED at one-loop order. We finally discuss the validity of using the RG as the proxy of one-loop effects on the top pair production. As an aside, we clarify the often-studied relations between top pair observables.