Decays of Fourth Generation Bound States

TL;DR

This paper analyzes the decay modes of hypothetical heavy fourth-generation quark bound states, highlighting dominant decay channels and narrow widths, with implications for heavy fermion-antifermion states due to Higgs exchange.

Contribution

It introduces the decay characteristics of fourth-generation quark bound states mediated by Higgs exchange, including dominant decay modes and narrow widths, extending to heavy leptons and neutrinos.

Findings

Vector states mainly decay via Higgs-gamma and Higgs-Z channels.

Pseudoscalar states predominantly decay through two-gluon mode.

Bound states are very narrow with widths less than 1% of binding energy.

Abstract

We consider the decay modes of the heavy $q^\prime\bar{q^\prime}$ bound states originating from Higgs boson exchange between quark -- anti-quark pair. In case of a small coupling between the fourth and lower generation the main decay mode is $q^\prime\bar{q^\prime}$ annihilation. We show that for a vector state the dominant decay modes are Higgs-gamma and Higgs-Z decays, while for a pseudoscalar state the strong two-gluon decay mode dominates. The bound states are very narrow. The ratio of the total width to the binding energy is less than 1% if we are not extremely close to the critical quark mass where the binding energy is very small. The discussed decay modes exist for any fermion-antifermion bound states including heavy leptons and heavy neutrinos if their masses are high enough to form a bound state due to attractive Higgs boson exchange potential.