Search for the rare decay of the W boson into a pion and a photon in proton-proton collisions at root s=13 TeV

The CMS collaboration, A. M. Sirunyan, A. Tumasyan, P. Eerola, Laurent Forthomme, H. Kirschenmann, K. Österberg, M. Voutilainen, Erik Brücken, F. Garcia, J. Havukainen, V. Karimäki, Minsuk Kim, R. Kinnunen, T. Lampén, K. Lassila-Perini, S. Lehti, T. Lindén, P. Luukka, Juska PekkanenH. Siikonen, E. Tuominen, J. Tuominiemi, Jussi Viinikainen, T. Tuuva

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A search is performed for the rare decay W-+/--> pi(+/-)gamma in proton-proton collisions at root s = 13 TeV. Data corresponding to an integrated luminosity of 137 fb(-1) were collected during 2016 to 2018 with the CMS detector. This analysis exploits a novel search strategy based on W boson production in top quark pair events. An inclusive search for the W-+/--> pi(+/-)gamma decay is not optimal at the LHC because of the high trigger thresholds. Instead, a trigger selection is exploited in which the W boson originating from one of the top quarks is used to tag the event in a leptonic decay. The W boson emerging from the other top quark is used to search for the W-+/--> pi(+/-)gamma signature. Such decays are characterized by an isolated track pointing to a large energy deposit, and by an isolated photon of large transverse momentum. The presence of b quark jets reduces the background from the hadronization of light-flavor quarks and gluons. The W-+/- -> pi(+/-)gamma decay is not observed. An upper exclusion limit is set to this branching fraction, corresponding to 1.50 x 10(-5) at 95% confidence level, whereas the expected upper exclusion limit is 0.85(-0.29)(+0.52) x 10(-5). (C) 2021 The Author(s). Published by Elsevier B.V.

TidskriftPhysics Letters B
Antal sidor24
StatusPublicerad - 10 aug. 2021
MoE-publikationstypA1 Tidskriftsartikel-refererad


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