Search for a resonance decaying to a W boson and a photon in proton-proton collisions at $\sqrt{s}$ = 13 TeV using leptonic W boson decays

TL;DR

This paper reports a search for a new charged resonance decaying into a W boson and a photon in proton-proton collisions at 13 TeV, setting new limits on its production cross section across a wide mass range.

Contribution

It introduces a novel search for a charged resonance decaying to W and photon, combining leptonic and hadronic W decay modes for improved constraints.

Findings

No significant excess observed above background.

Set the most stringent upper limits to date on the resonance production cross section.

Combined analysis reduces upper limits for a 2.0 TeV resonance.

Abstract

A search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. Particle X has electric charge $\pm$ 1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%).