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

TL;DR

This paper reports a search for a hypothetical right-handed W boson and heavy neutrino in proton-proton collisions at 13 TeV, setting new limits on their masses with no observed excess over the standard model background.

Contribution

The study provides the most stringent limits to date on the mass of the right-handed W boson using CMS data at 13 TeV, exploring both merged and separated decay topologies.

Findings

No significant excess observed over background.

Excluded W$_\mathrm{R}$ masses up to 4.8-5.4 TeV depending on the channel.

Set new upper limits on W$_\mathrm{R}$ production cross sections.

Abstract

A search is presented for a right-handed W boson (W$_\mathrm{R}$) and a heavy neutrino (N), in a final state consisting of two same-flavor leptons (ee or $\mu\mu$) and two quarks. The search is performed with 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 138 fb$^{-1}$. The search covers two regions of phase space, one where the decay products of the heavy neutrino are merged into a single large-area jet, and one where the decay products are well separated. The expected signal is characterized by an excess in the invariant mass distribution of the final-state objects. No significant excess over the standard model background expectations is observed. The observations are interpreted as upper limits on the product of W$_\mathrm{R}$ production cross sections and branching fractions assuming that couplings are identical to those of the standard model W boson. For N masses $m_\mathrm{N}$ equal to half the W$_\mathrm{R}$ mass $m_\mathrm{W_R}$ ($m_\mathrm{N}$ = 0.2 TeV), $m_\mathrm{W_R}$ is excluded at 95% confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channels, respectively. This analysis provides the most stringent limits on the W$_\mathrm{R}$ mass to date.