Measuring CP-Violating Observables in Rare Top Decays at the LHC

TL;DR

This paper investigates CP-violating effects in rare top quark decays at the LHC, proposing observables and analysis methods to detect and measure new physics contributions in these processes.

Contribution

It introduces two specific CP-violating observables for top decays and evaluates their effectiveness using Monte Carlo simulations, advancing methods for new physics detection.

Findings

Partial-rate asymmetry effectively measures new-physics parameters.

Triple-product correlations can be used to extract specific new-physics combinations.

Detection strategies show promising sensitivity at the LHC.

Abstract

In this paper we consider CP-violating new-physics contributions to the decay $t \to b \bar b c$. We examine the prospects for detecting such new physics at the LHC, which requires studying the process $gg \to t (\to b \bar b c) \bar t (\to \bar b \ell \bar \nu)$. We find two observables that can be used to reveal the presence of CP-violating new physics in $t \to b \bar b c$. They are (i) the partial-rate asymmetry and (ii) the triple-product correlations involving the momenta of various particles associated with the interaction. A Monte Carlo analysis is performed to determine how well these observables can be used to detect the presence of new physics, and to measure its parameters. We find that there is little difficulty in extracting the value of the relevant new-physics parameter from the partial-rate asymmetry. For the triple-product correlations, we test multiple strategies that can be used for the extraction of the corresponding combination of new-physics parameters.