Early LHC Phenomenology of Yukawa-bound Heavy Q\bar{Q} Mesons

TL;DR

This paper explores the potential formation and detection of Yukawa-bound heavy Qar{Q} mesons at the LHC, focusing on their properties, decay modes, and experimental signatures for quarks with masses between 500 and 700 GeV.

Contribution

It introduces a relativistic bound state approach to study Yukawa-bound heavy quark mesons and predicts distinctive production and decay signatures relevant for LHC searches.

Findings

Predicted a color octet, isosinglet vector meson ('gluon-prime') production via qar{q} annihilation.

Identified dominant decay modes including C8_8^\u00b0W^\u00b0, C8_8^0Z^0, and constituent quark decay.

Suggested experimental signatures such as WWg with high multiplicity and jet substructures.

Abstract

Current limits from the LHC on fourth generation quarks are already at the unitarity bound of 500 GeV or so. If they exist, the strong Yukawa couplings are turning nonperturbative, and may form bound states. We study the domain of m_{b'} and m_{t'} in the range of 500 to 700 GeV, where we expect binding energies are mainly of Yukawa origin, with QCD subdominant. To be consistent with electroweak precision tests, the t' and b' quarks have to be nearly degenerate, exhibiting a new "isospin". Comparing relativistic expansion with a relativistic bound state approach, we find the most interesting is the production of a color octet, isosinglet vector meson (a "gluon-prime") via q\bar{q} to \omega_8. Leading decay modes are \pi_8^\pm W^\mp, \pi_8^0Z^0, and constituent quark decay, with q\bar{q} and t\bar{t}' and b\bar{b}' subdominant. The color octet, isovector pseudoscalar \pi_8 meson decays via constituent quark decay, or to Wg. These decay rates are parameterized by the decay constant, the binding energy and mass differences, and V_{tb'}. For small V_{t'b}, one could have a spectacular signal of WWg, where a soft W accompanies a very massive Wg pair. In general, however, one has high multiplicity signals with b, W and t jet substructures that are not so different from t'\bar{t}' and b'\bar{b}' search.