# Search for $W$ Boson Decays to Three Charged Pions

19 April 2019

Abstract: For the first time, a search for the rare decay of the $W$ boson to three charged pions has been performed. Proton-proton collision data recorded by the CMS experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $77.3\text{}\text{}{\mathrm{fb}}^{-1}$, have been analyzed. No significant excess is observed above the background expectation. An upper limit of $1.01×{10}^{-6}$ is set at 95% confidence level on the branching fraction of the $W$ boson to three charged pions. This provides a strong motivation for theoretical calculations of this branching fraction.

Published in: Physical Review Letters 122 (2019)