Search for heavy neutral leptons in top quark decays with same-sign, same-flavor dilepton final states in proton-proton collisions at √s = 13 TeV
Abstract
A search for a Majorana-type heavy neutral lepton (HNL) produced in top quark decays is reported. The search is based on proton-proton collision data at √s = 13 TeV, corresponding to an integrated luminosity of 138 fb−1, collected during 2016−2018 with the CMS detector at the CERN LHC. In the type-I seesaw model, a Majorana HNL can mediate lepton-number-violating top quark decays. The search targets top quark pair production events in which one top quark decays into a bottom quark and a W boson, which subsequently decays into a charged lepton (electron or muon) and an HNL. The Majorana HNL then decays into a W boson and a charged lepton with the same sign and flavor as the one produced with the HNL. The experimental signature features a same-sign, same-flavor lepton pair and jets. The HNL masses between 20 and 100 GeV are probed. The data agree with the standard model background prediction. Observed (expected) upper limits at 95% confidence level are set on the branching fraction of the top quark decay into an HNL, a charged lepton, and a bottom quark, varying between [1.1 (0.71)] ×10−5 and [4.8 (3.0)] ×10−5 in the dielectron channel, and between [3.7 (3.4)] ×10−6 and [2.4 (1.3)] ×10−5 in the dimuon channel.
Related
- Search for long-lived heavy neutral leptons in signatures with one prompt muon and a secondary vertex formed by two non-prompt muons in proton-proton collisions at √s = 13 and 13.6 TeV
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- Search for supersymmetric particle pair production in final states with two oppositely charged leptons and large missing transverse momentum in proton-proton collisions at √s = 13 TeV
- Search for Higgs boson compositeness effects in high-mass dilepton final states in proton-proton collisions at √s = 13 and 13.6 TeV
- Search for a resonance in events with four top quarks decaying into two leptons and jets in proton-proton collisions
BibTeX
@misc{collaboration2026search,
title = {{Search for heavy neutral leptons in top quark decays with same-sign, same-flavor dilepton final states in proton-proton collisions at $\sqrts$ = 13 TeV}},
author = {CMS Collaboration},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.04904},
eprint = {2611.04904},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.04904},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Search for heavy neutral leptons in top quark decays with same-sign, same-flavor dilepton final states in proton-proton collisions at √s = 13 TeV
AU - CMS Collaboration
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.04904
UR - https://arxiv.org/abs/2611.04904
AB - A search for a Majorana-type heavy neutral lepton (HNL) produced in top quark decays is reported. The search is based on proton-proton collision data at √s = 13 TeV, corresponding to an integrated luminosity of 138 fb^−1, collected during 2016−2018 with the CMS detector at the CERN LHC. In the type-I seesaw model, a Majorana HNL can mediate lepton-number-violating top quark decays. The search targets top quark pair production events in which one top quark decays into a bottom quark and a W boson, which subsequently decays into a charged lepton (electron or muon) and an HNL. The Majorana HNL then decays into a W boson and a charged lepton with the same sign and flavor as the one produced with the HNL. The experimental signature features a same-sign, same-flavor lepton pair and jets. The HNL masses between 20 and 100 GeV are probed. The data agree with the standard model background prediction. Observed (expected) upper limits at 95% confidence level are set on the branching fraction of the top quark decay into an HNL, a charged lepton, and a bottom quark, varying between [1.1 (0.71)] ×10^−5 and [4.8 (3.0)] ×10^−5 in the dielectron channel, and between [3.7 (3.4)] ×10^−6 and [2.4 (1.3)] ×10^−5 in the dimuon channel.
ER -