Implications of the CMS search for W_R on Grand Unification

TL;DR

This paper reinterprets CMS's 2.8σ excess in the context of left-right symmetric models and SO(10) grand unification, exploring implications for gauge couplings, symmetry breaking, and potential observable phenomena like neutron oscillations.

Contribution

It provides a detailed analysis of the CMS excess within grand unified theories, identifying specific symmetry-breaking sequences and constraints on gauge couplings and scales.

Findings

A TeV-scale W_R is compatible with certain model conditions.

The symmetry-breaking sequence is uniquely determined under minimal assumptions.

Proton decay detection is unlikely due to high unification scale.

Abstract

The CMS experiment at the Large Hadron Collider has reported a 2.8$\sigma$ excess in the $(2e)(2jets)$ channel around 2.1 TeV. Interpretation of this data is reconsidered in terms of the production of a right-handed weak gauge boson, $W_R$, of the left-right symmetric model and in an $SO(10)$ grand unified theory abiding by the Extended Survival Hypothesis. The left-right symmetric model can be consistent with this excess if (a) the heavy right-handed neutrino has a mass near $W_R$, or (b) if $g_L \neq g_R$, or (c) the right-handed CKM matrix is nontrivial. Combinations of the above possibilities are also viable. A $W_R$ with a mass in the TeV region if embedded in $SO(10)$ is not compatible with $g_L = g_R$. Rather, it implies $0.64 \leq g_R/g_L \leq 0.78$. Further, a unique symmetry-breaking route -- the order being left-right discrete symmetry breaking first, followed by $SU(4)_C$ and finally $SU(2)_R$ -- to the standard model is picked out. The $L \leftrightarrow R$ discrete symmetry has to be broken at around $10^{16}$ GeV. The grand unification scale is pushed to $10^{18}$ GeV making the detection of proton decay in ongoing searches rather unlikely. The $SU(4)_C$ breaking scale can be at its allowed lower limit of $10^6$ GeV so that $n - \bar{n}$ oscillation or flavour changing processes such as $K_L \rightarrow \mu e$ and $B_{d,s} \rightarrow \mu e$ may be detectable. The Higgs scalar multiplets responsible for $SO(10)$ symmetry breaking at various stages are uniquely identified so long as one adheres to a minimalist principle. We also remark, {\em en passant}, about a partially unified Pati-Salam model.