Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton

(CMS Collaboration) Giljanović, Duje; Godinović, Nikola; Lelas, Damir; Šćulac, Ana; Bargassa, Pedrame; Brigljević, Vuko; Chitroda, Bhakti Kanulal; Bhakti, Kanulal; Ferenček, Dinko; Mishra, Saswat; Starodumov, Andrey; Šuša, Tatjana (2024) Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton. The Journal of high energy physics, 03 . ISSN 1126-6708

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Abstract

A search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2-20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb . A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths to each lepton generation and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of 5 (4) 10 are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm.

Item Type:	Article
Uncontrolled Keywords:	High energy physics ; Experimental particle physics ; LHC ; CMS ; Beyond Standard Model ; Hadron-Hadron Scattering ; Lifetime ; p p: colliding beams ; lepton: flavor ; final state: hadronic ; muon: coupling ; p p: scattering ; neutrino: heavy ; decay: length ; neutrino: mass ; neutrino: lifetime ; neutral particle: long-lived ; background ; network ; CERN Lab ; final state: ((n)jet dilepton) ; electron ; CERN LHC Coll ; conservation law ; constituent ; neutrino: Majorana ; neutrino: Dirac
Subjects:	NATURAL SCIENCES > Physics
Divisions:	Division of Experimental Physics
Depositing User:	Vuko Brigljević
Date Deposited:	11 Oct 2024 14:30
URI:	http://fulir.irb.hr/id/eprint/9158
DOI:	10.1007/JHEP03(2024)105

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