TeV Window to Grand Unification: Higgs's Light Color Triplet Partner

TL;DR

This work shows that the color-triplet partner of the Higgs, $T$, can remain light at the TeV scale if high-dimensional operators involving the adjoint $24_H$ decouple the SU(5) Yukawa relations, enabling direct collider tests while keeping proton- and neutron-number-violating effects within bounds. By treating the $T$ couplings to quarks and leptons as free parameters, the authors derive a set of correlated observables: proton-decay channels and lifetimes, neutron oscillations into sterile neutrinos, and neutron–antineutron transitions, all tied to the same underlying $T$-exchange dynamics. They show that current proton-decay constraints imply strong limits on combinations of $g_{Tud}, g_{TQQ}, g_{TQL}, g_{Td u}$, and predict resonant neutron-to-sterile-neutrino oscillations with lifetimes of order $10^{2}-10^{3}$ s that cold-neutron experiments could probe; in the collider context, TeV-scale $T$ can hadronize into $T$-baryons or $T$-mesons and decay with displacement to $qq$ or $q\nu^c$, offering observable signatures at the LHC. The framework thus provides a coherent, multi-pronged testing ground for Grand Unification across high-energy colliders and low-energy precision experiments, and its essential ideas extend to larger GUTs and supersymmetric realizations.

Abstract

The color-triplet partner of the Higgs doublet, called a $T$-particle, is a universal feature of Grand Unification. It has been shown some time ago that this particle can be accessible for direct production in collider experiments. In this paper we point out that the $T$-particle represents a simultaneous low-energy probe of baryon number violation as well as of the origin of the neutrino mass, linking the mediation of proton decay with oscillations of the neutron into a sterile neutrino. We point out a triple correlation between its collider signatures, proton decay measurements and the searches for the magnetic resonance disappearance of free neutrons in cold neutron experiments. In this way, the $T$-particle can provide a diversity of correlated experimental windows into Grand Unification.

Figures (6)

• Figure 1: An example of a proton decay process mediated via the $T$-particle.
• Figure 2: Examples of diagrams responsible for proton decay into a pion and an active neutrino via different couplings.
• Figure 3: Double proton decay
• Figure 4: Examples of diagrams mixing neutron with sterile neutrino via different couplings.
• Figure 5: An example of a diagram generating the neutron-antineutron transition.