Search for New Physics in Rare Top Decays: $t \bar t$ Spin Correlations and Other Observables

TL;DR

This paper investigates potential new physics in rare top quark decays by identifying observables in $t ar t$ production at the LHC that could reveal deviations from the Standard Model, focusing on decay distributions and spin correlations.

Contribution

It introduces six specific observables, including invariant mass and angular correlations, to detect new physics effects in top quark decay processes at the LHC.

Findings

Six observables identified for new physics detection.

Angular correlations linked to $t ar t$ spin correlations.

Potential to distinguish new physics in top decays.

Abstract

In this paper we study new-physics contributions to the top-quark decay $t \to b \bar b c$. We search for ways of detecting such new physics via measurements at the LHC. As top quarks are mainly produced at the LHC in $t \bar t$ production via gluon fusion, we analyze the process $gg \to t \bar t \to (b \bar b c) (\bar b \ell \bar \nu)$. We find six observables that can be used to reveal the presence of new physics in $t \to b \bar b c$. Three are invariant mass-squared distributions involving two of the final-state particles in the top decay, and three are angular correlations between the final-state quarks coming from the $t$ decay and the $\ell^-$ coming from the $\bar t$ decay. The angular correlations are related to the $t \bar t$ spin correlation.