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

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.

Comments: Published version