Karlsruhe 2024 – scientific programme
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T: Fachverband Teilchenphysik
T 52: Search for new particles 4 (leptoquarks, LHC)
T 52.5: Talk
Wednesday, March 6, 2024, 17:00–17:15, Geb. 20.30: 1.067
Search for heavy right-handed Majorana neutrinos in tt decays — •Tongbin Zhao1,2, Diptaparna Biswas1, Beatrice Cervato1, Markus Cristinziani1, Carmen Diez Pardos1, Ivor Fleck1, Arpan Ghosal1, Gabriel Gomes1, Jan Joachim Hahn1, Vadim Kostyukhin1, Nils Krengel1, Buddhadeb Mondal1, Katharina Voss1, Wolfgang Walkowiak1, and Adam Warnerbring1 — 1Experimentelle Teilchenphysik, Center for Particle Physics Siegen, Universität Siegen — 2Shandong University, China
A search for heavy right-handed Majorana neutrinos is performed with the Run-2 dataset recorded from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider and is based on √s=13 TeV proton-proton collision data with an integrated luminosity of 140.1 fb−1. The targeted process is t t : one of the top quarks decays into a pair of same-sign same-flavour leptons (electrons or muons), a b-quark and two light quarks, while the other decays into a b-quark and two light quarks. The final states feature same-sign dilepton signatures. This analysis is the first search for heavy neutrinos with t t events at the mass range of 15−75 GeV.
The multivariate analysis is performed to set the signal region to improve the significance. Besides, several control regions are defined to estimate the main backgrounds from the ttbar +X samples. After performing the statistical analysis with profile likelihood fit, we could set the best limits on the mixing parameter of e e / µ µ channel at the mass region of 15−75 GeV.
Keywords: Heavy neutrino; BSM; Majorana neutrino