CMS-PAS-EXO-21-002

CMS-PAS-EXO-21-002
Inclusive nonresonant multilepton probes of new phenomena at $\sqrt{s}= $ 13 TeV
CMS Collaboration
August 2021

Abstract: An inclusive search for nonresonant signatures of beyond the standard model phenomena in events with three or more charged leptons, including hadronic decays of tau leptons, is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 138 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}= $ 13 TeV, collected with the CMS detector at the LHC in 2016-2018. Events are categorized based on the charge and flavor multiplicities of the leptons, the multiplicity of b tagged jets, and various kinematic variables. Three scenarios of physics beyond the standard model are probed, viz. the pair production of type-III seesaw heavy fermions with arbitrary couplings to leptons of any flavor, vector-like leptons with couplings to tau leptons, and third generation leptoquarks with flavor-diagonal or cross-generational couplings involving top quarks and charged leptons. Optimal separation between signal and standard model background processes is achieved by the use of signal-specific boosted decision trees. No significant deviations from the background expectations are observed. Lower limits are set at 95% confidence level on the masses of type-III seesaw heavy fermions at 890 GeV for any branching fraction combination to standard model leptons. Scalar leptoquarks decaying exclusively to a top quark and a lepton of any flavor are excluded for masses below 1120 GeV. Doublet and singlet vector-like tau lepton extensions of standard model are excluded for masses below 1045 GeV and in mass range of 125-170 GeV, respectively. Detailed results are also presented to facilitate alternative theoretical interpretations.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRD. The superseded preliminary plots can be found here.

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