The S-wave topped meson

TL;DR

This paper investigates the mass spectrum and properties of S-wave topped mesons containing a single top quark using Bethe-Salpeter formalism, predicting their masses, lifetimes, and potential observability at the LHC.

Contribution

It provides the first detailed theoretical predictions of the mass spectrum and decay characteristics of S-wave topped mesons with a novel Bethe-Salpeter approach.

Findings

Masses of topped mesons are close to the top-quark mass.

Mass differences for $t\bar{b}$ states range from 5.08 to 5.74 GeV.

Mass differences for $t\bar{c}$ states range from 1.90 to 2.60 GeV.

Abstract

Inspired by the recent observation of the near-threshold enhancement in top-quark pair production by CMS and ATLAS, we investigate the mass spectrum of S-wave topped meson which containing a single top quark, i.e., $t\bar{q}$, $t\bar{c}$, and $t\bar{b}$, in the framework of Bethe-Salpeter formalism. These states are expected to exhibit significantly enhanced lifetimes and correspondingly narrower decay widths compared to toponium, primarily because only a single top quark participates in the weak decay process. The numerical results indicate that the masses of topped mesons are close to the top-quark mass. For the $t\bar{b}$ states, the $1S$ state is approximately 5.08~GeV heavier than the top quark, while the $2S$, $3S$, and $4S$ states are about 5.37~GeV, 5.57~GeV, and 5.74~GeV heavier, respectively. For the $t\bar{c}$ states, the corresponding mass differences are 1.90~GeV, 2.23~GeV, 2.45~GeV, and 2.60~GeV. The possible production and decay properties are also analyzed, which could be measured in LHC experiments.