A search for charged-lepton flavour violation (CLFV) in top quark (t) production and decay is presented. The search uses proton-proton collision data corresponding to 138 fb(-1) collected with the CMS experiment at root s = 13TeV. The signal consists of the production of a single top quark via a CLFV interaction or top quark pair production followed by a CLFV decay. The analysis selects events containing a hadronically decaying tau lepton and a muon of opposite electric charge, as well as at least three jets, one of which is identified as originating from the fragmentation of a bottom quark. Machine learning classification techniques are used to distinguish signal from standard model background events. The results of this search are consistent with the standard model expectations. The upper limits at 95% confidence level on the branching fraction B for CLFV top quark decays to a muon, a tau lepton, and an up or a charm quark are set at B(t -> mu tu) < (0.04, 0.08, and 0.12) x 10(-6), and B(t -> mu tc) < (0.81, 1.71, and 2.05) x 10(-6) for scalar, vector, and tensor-like operators, respectively.

Search for charged-lepton flavour violation in top quark interactions with an up-type quark, a muon, and a τ lepton in proton-proton collisions at $$\sqrt{s}={13}$$ TeV

Alexe, C.;Bruschini, D.;Ligabue, F.;
2025

Abstract

A search for charged-lepton flavour violation (CLFV) in top quark (t) production and decay is presented. The search uses proton-proton collision data corresponding to 138 fb(-1) collected with the CMS experiment at root s = 13TeV. The signal consists of the production of a single top quark via a CLFV interaction or top quark pair production followed by a CLFV decay. The analysis selects events containing a hadronically decaying tau lepton and a muon of opposite electric charge, as well as at least three jets, one of which is identified as originating from the fragmentation of a bottom quark. Machine learning classification techniques are used to distinguish signal from standard model background events. The results of this search are consistent with the standard model expectations. The upper limits at 95% confidence level on the branching fraction B for CLFV top quark decays to a muon, a tau lepton, and an up or a charm quark are set at B(t -> mu tu) < (0.04, 0.08, and 0.12) x 10(-6), and B(t -> mu tc) < (0.81, 1.71, and 2.05) x 10(-6) for scalar, vector, and tensor-like operators, respectively.
2025
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
Beyond Standard Model; Hadron-Hadron Scattering; Tau Physics; Top Physics
   Search for Higgs bosons decaying to charm quarks
   HIGCC
   European Commission
   Horizon 2020 Framework Programme
   724704

   Majorana neutrino discovery strategy with CMS
   MajorNet
   European Commission
   Horizon 2020 Framework Programme
   758316

   International Training Network for Statistics in High Energy Physics and Society
   INSIGHTS
   European Commission
   Horizon 2020 Framework Programme
   765710

   Advanced Multi-Variate Analysis for New Physics Searches at the LHC
   AMVA4NewPhysics
   European Commission
   Horizon 2020 Framework Programme
   675440
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/160547
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