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

Journal Article · Sun Dec 01 00:00:00 EST 2019 · Physics Letters. B

DOI:https://doi.org/10.1016/j.physletb.2019.135052· OSTI ID:1573273

Das, Arindam; Dev, P. S. Bhupal; Okada, Nobuchika

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 ($$Z^\prime$$) 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 ($$m_{\rm lightest}$$). We find that for $$m_{\rm lightest}\lesssim 10^{-5}$$ 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 long-lived 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.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-07CH11359
• OSTI ID: 1573273
• Alternate ID(s): OSTI ID: 1546016
• Report Number(s): arXiv:1906.04132; FERMILAB-PUB-19-268-T; S0370269319307749; 135052; PII: S0370269319307749
• Journal Information: Physics Letters. B, Journal Name: Physics Letters. B Vol. 799 Journal Issue: C; ISSN 0370-2693
• Publisher: Elsevier
• Country of Publication: Netherlands
• Language: English

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