Search for a right-handed W boson and heavy neutrino in proton-proton collisions at $\sqrt{s}=13$ TeV

A search for a right-handed $\mathrm{W}$ boson ($\mathrm{W_{R}}$) and a heavy neutrino, in a final state consisting of two same-flavor leptons ($\mathrm{e}$ or $\mu$) and two quarks, is presented. The search is performed by the CMS experiment at the CERN LHC using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of $137\,\text{fb}^{-1}$. The search covers both regions of phase space where the decay products of the heavy neutrino are merged into a single large-area jet and where the decay products are well-separated. The expected signal is characterized by an excess above the prediction from the standard model in the invariant mass distribution of the final-state objects. The observations are interpreted as upper limits on the products of $\mathrm{W_{R}}$ production cross sections and branching fractions assuming that couplings are identical to those of the standard model for the $\mathrm{W}$ boson. For $m_\mathrm{N}=1/2m_{\mathrm{W_{R}}}$ ($m_\mathrm{N}=200$ ), the mass of the $\mathrm{W_{R}}$ is excluded at $95\%$ confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channel, respectively. The maximum observed local significance is in the electron channel and is 2.95 standard deviations for a signal with $(m_{\mathrm{W_{R}}}, m_\mathrm{N}) = (6000, 800)$ GeV, corresponding to a global significance of 2.78 $\sigma$. This analysis provides the most stringent limits on the $\mathrm{W_{R}}$ mass to date.