Search for a heavy composite Majorana neutrino in events with dilepton signatures from proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
CMS-EXO-20-011, 2022.

Abstract (data abstract)
Results are presented of a search for a heavy Majorana neutrino $\mathrm{N}_{\ell}$ decaying into two same-flavor leptons $\ell$ (electrons or muons) and a quark-pair jet. A model is considered in which the $\mathrm{N}_{\ell}$ is an excited neutrino in a compositeness scenario. The analysis is performed using a sample of proton-proton collisions at $\sqrt{s}=13\TeV$ recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138~\fbinv. The data are found to be in agreement with the standard model prediction. For the process in which the $\mathrm{N}_{\ell}$ is produced in association with a lepton, followed by the decay of the $\mathrm{N}_{\ell}$ to a same-flavor lepton and a quark pair, an upper limit at $95\%$ confidence level on the product of the cross section and branching fraction is obtained as a function of the $\mathrm{N}_{\ell}$ mass $m_{\mathrm{N}_{\ell}}$ and the compositeness scale $\Lambda$.For this model the data exclude the existence of $\mathrm{N}_{\mathrm{e}}$ ($\mathrm{N}_{\PGm}$)for $m_{\mathrm{N}_{\ell}}$ below 6.0\,(6.1)\TeV at the limit where $m_{\mathrm{N}_{\ell}}$ is equal to $\Lambda$. For $m_{\mathrm{N}_{\ell}}\approx1\TeV$, values of $\Lambda$ less than 20\,(23)\TeV are excluded.These results represent a considerable improvement in sensitivity, covering a larger parameter space than previous searches in $\Pp\Pp$ collisions at 13\TeV.

  • Cut-flow table

    Additional material

    10.17182/hepdata.133151.v1/t1

    Cut-flow table mN=0.5TeV, electron, muon channel, 2018.

  • Figure 4a

    Data from Figure 4 (upper left).

    10.17182/hepdata.133151.v1/t2

    Distributions of \mllj for the data, and the post-fit backgrounds (stacked histograms), in the SRs of the \eeqq channel. The...

  • Figure 4b

    Data from Figure 4 (upper right).

    10.17182/hepdata.133151.v1/t3

    Distributions of \mllj for the data, and the post-fit backgrounds (stacked histograms), in the SRs of the \mmqq channel. The...

  • Theoretical cross-sections table

    Additional material for Figures 5 a,b

    10.17182/hepdata.133151.v1/t4

    Theoretical cross-sections for heavy composite majorana neutrino signals for $\Lambda$=13 TeV.

  • Figure 5a

    Data from Figure 5a.

    10.17182/hepdata.133151.v1/t5

    Exclusion limits on the product of cross section and branching fraction for the electron channel, as a function of the...

  • Figure 5b

    Data from Figure 5b.

    10.17182/hepdata.133151.v1/t6

    Exclusion limits on the product of cross section and branching fraction for the muon channel, as a function of the...

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