Using t -> b \bar{b} c to Search for New Physics

TL;DR

This paper explores how new physics could influence the decay t -> b ar{b} c, proposing measurements of various asymmetries and partial widths as indicators of physics beyond the Standard Model.

Contribution

It introduces a comprehensive effective Lagrangian framework with 10 Lorentz structures to analyze NP effects in top quark decay and identifies measurable asymmetries that signal NP presence.

Findings

NP can significantly alter decay partial widths and asymmetries.

Asymmetries can reach 10-20% in the presence of NP.

Results are applicable to similar decays involving s quarks.

Abstract

We consider new-physics (NP) contributions to the decay t -> b \bar{b} c. We parameterize the NP couplings by an effective Lagrangian consisting of 10 Lorentz structures. We show that the presence of NP can be detected through the measurement of the partial width. A partial identification of the NP can be achieved through the measurements of a forward-backward-like asymmetry, a top-quark-spin-dependent asymmetry, the partial rate asymmetry, and a triple-product asymmetry. These observables, which vanish in the standard model, can all take values in the 10-20% range in the presence of NP. Since |V_{tb}V_{cb}| \simeq |V_{ts} V_{cs}|, most of our results also hold, with small changes, for t -> s \bar{s} c.