CMS-PAS-EXO-20-011

CMS-PAS-EXO-20-011
Search for a heavy composite Majorana neutrino
CMS Collaboration
March 2022

Abstract: This note describes a search for a heavy Majorana neutrino $\mathrm{N}_{\ell}$ in the final state with two same-flavor leptons $\ell$ (electrons or muons) and two quarks. In the model considered, $\mathrm{N}_{\ell}$ arises from a composite scenario. The analysis is performed using a sample of proton-proton collisions at $\sqrt{s}=$ 13 TeV recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138 fb $^{-1}$ . The observed data are in agreement with the standard model prediction. For a process in which $\mathrm{N}_{\ell}$ is produced in association with a lepton, followed by the decay of $\mathrm{N}_{\ell}$ to a same-flavor lepton and a quark pair, an upper limit at 95% confidence level on the cross section times branching fraction is obtained as a function of the $\mathrm{N}_{\ell}$ mass $m_{\mathrm{N}_{\ell}}$ . In this model, the data exclude $\mathrm{N}_{\mathrm{e}}$ ( $\mathrm{N}_{\mu}$ ) for $m_{\mathrm{N}_{\ell}}$ below 5.50 (5.70) TeV in the limit where the compositeness scale $\Lambda$ is equal to $m_{\mathrm{N}_{\ell}}$ , and below 5.10 (5.50) TeV with the more restrictive requirement that the unitarity bound is satisfied over the full phase space of parton motion within the proton.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Accepted by PLB. The superseded preliminary plots can be found here.

CMS Publications