Long-lived TeV-scale right-handed neutrino production at the LHC in gauged U(1) model

Abstract

A gauged U (1) X extension of the Standard Model is a simple and consistent framework to naturally incorporate three right-handed neutrinos (RHNs) for generating the observed light neutrino masses and mixing by the type-I seesaw mechanism. We examine the collider testability of the U (1) X model, both in its minimal form with the conventional charges, as well as with an alternative charge assignment, via the resonant production of the U (1) X gauge boson (Z ) and its subsequent decay into a pair of RHNs. We first derive an updated upper limit on the new gauge coupling g X as a function of the Z -boson mass from the latest LHC dilepton searches. Then we identify the maximum possible cross section for the RHN pair-production under these constraints. Finally, we investigate the possibility of having one of the RHNs long-lived, even for a TeV-scale mass. Employing the general parametrization for the light neutrino mass matrix to reproduce the observed neutrino oscillation data, we perform a parameter scan and find a simple formula for the maximum RHN lifetime as a function of the lightest neutrino mass eigenvalue (m lightest ). We find that for m lightest 10 −5 eV, one of the RHNs in the minimal U (1) X scenario can be long-lived with a displaced-vertex signature which can be searched for at the LHC and/or with a dedicated longlived particle detector, such as MATHUSLA. In other words, once a long-lived RHN is observed, we can set an upper bound on the lightest neutrino mass in this model.

Heavy neutral leptons at ANUBIS

“…The model variant we will be using in our numerical estimate and its implications for accelerator searches has been discussed recently in Refs. [27,28,[35][36][37]. Apart from the HNLs, the model predicts a Z 0 and (at least) a second Higgs.…”

Neutrino non-standard interactions: A status report

“…However, the scale of new physics behind the neutrino mass generation mechanism can be anywhere. Despite numerous searches for neutrino mass models (at TeV scale) at high-energy colliders [24,112,113,117,118,[185][186][187][188][189][190][191][192][193][194][195][196][197][198], no compelling evidence has been found so far. Then, the following question may arise.…”

Neutrino and Z′ phenomenology in an anomaly-free U(1) extension: role of higher-dimensional operators

“…Also possible are the trilepton plus jets and the four-lepton final states, albeit with smaller cross sections. Many of these have been studied extensively, not only in the context of many popular new physics scenarios (such as supersymmetry or theories defined in higher dimensions), but also in those similar to ours [88][89][90][91][92][93][94][95]. A simple scaling of the cross sections convinces one that the parameter space required for reproducing the neutrino masses and mixings would be accessible only once the high-luminosity version of the LHC is operational.…”