Sirunyan, A. M.Tumasyan, A.Adam, W.Ambrogi, F.Asilar, E.Bergauer, T.Brandstetter, J.2025-03-232025-03-2320190031-90071079-7114https://doi.org/10.1103/PhysRevLett.122.151802https://hdl.handle.net/11486/5510For 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 fb(-1), have been analyzed. No significant excess is observed above the background expectation. An upper limit of 1.01 x 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.eninfo:eu-repo/semantics/openAccessPair ProductionArticle1221510.1103/PhysRevLett.122.151802310505192-s2.0-85065556806Q1WOS:000465182200002Q1