Energy correlation of bottom quarks from decays of top quarks in electron$-$positron annihilation

TL;DR

This paper investigates the energy correlations of bottom quarks from top quark decays in electron-positron collisions, focusing on CP-violation effects and their potential observability at future colliders.

Contribution

It introduces a detailed analysis of CP-violating energy asymmetries in bottom quark pairs from top decays, including one-loop calculations of anomalous couplings constrained by recent experimental data.

Findings

Energy asymmetries depend on collision energy up to 1.2 TeV.

CP-violating couplings can produce measurable asymmetries.

Behavior of asymmetries varies with energy, offering potential signals for new physics.

Abstract

Joint energy distribution of the bottom quark and antiquark from decays of the top quark and antiquark produced in the reaction $e^+ e^- \to t \bar{t}$ is studied. Main emphasis is put on $CP$-violation effects in the interaction of the photon and $Z$ boson with the top quarks. Energy asymmetries of $b$ and $\bar{b}$ quarks, which give access to the $CP$-violating terms, are considered. To estimate the magnitude of these asymmetries, the $CP$-violating $\gamma t t $ and $Z t t$ couplings are calculated in one-loop model with exchange of the Higgs boson with the mass of $125$ GeV. Interaction of this boson with the top quarks is assumed to include scalar and pseudoscalar couplings. Values of these couplings are constrained from the recent CMS analysis. Energy dependence of the asymmetries of $b$ and $\bar{b}$ quarks is calculated up to $\sqrt{s}=1.2$ TeV and some interesting features of their behavior are observed. These observables can be of interest for future studies at electron$-$positron colliders CLIC and ILC.