Search for long-lived heavy neutral leptons decaying in the CMS muon detectors in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
Phys.Rev.D 110 (2024) 012004, 2024.

Abstract (data abstract)
A search for heavy neutral leptons (HNLs) decaying in the CMS muon system is presented. A data sample is used corresponding to an integrated luminosity of 138\fbinv of proton-proton collisions at $\sqrt{s}=13\TeV$, recorded at the CERN LHC in 2016--2018. Decay products of long-lived HNLs could interact with the shielding materials in the CMS muon system and create hadronic and electromagnetic showers detected in the muon chambers. This distinctive signature provides a unique handle to search for HNLs with masses below 4\GeV and proper decay lengths of the order of meters. The signature is sensitive to HNL couplings to all three generations of leptons. Candidate events are required to contain a prompt electron or muon originating from a vertex on the beam axis and a displaced shower in the muon chambers. No significant deviations from the standard model background expectation are observed. In the electron (muon) channel, the most stringent limits to date are set for HNLs in the mass range of 2.1--3.0 (1.9--3.3)\GeV, reaching mixing matrix element squared values as low as $8.6\,(4.6) \times10^{-6}$.

  • Figure2 - CSC N hits

    Figure 2

    10.17182/hepdata.146757.v1/t1

    Distribution of $N_{hits}$ and $\Delta\phi_{lep}$ for DT clusters and CSC clusters in the electron channel. Signal distribution of a Majorana...

  • Figure2 - DT N hits

    Figure 2

    10.17182/hepdata.146757.v1/t2

    Distribution of $N_{hits}$ and $\Delta\phi_{lep}$ for DT clusters and CSC clusters in the electron channel. Signal distribution of a Majorana...

  • Figure2 - DT dphi

    Figure 2

    10.17182/hepdata.146757.v1/t3

    Distribution of $N_{hits}$ and $\Delta\phi_{lep}$ for DT clusters and CSC clusters in the electron channel. Signal distribution of a Majorana...

  • Figure4 - CSC clusters

    Figure 4

    10.17182/hepdata.146757.v1/t4

    Comparison of hits distributions for events with muons from \zmm between data and simulation, for CSC clusters (left) and DT...

  • Figure4 - DT clusters

    Figure 4

    10.17182/hepdata.146757.v1/t5

    Comparison of hits distributions for events with muons from \zmm between data and simulation, for CSC clusters (left) and DT...

  • Figure5

    Figure 5

    10.17182/hepdata.146757.v1/t6

    The expected and observed number of events in the signal region (bin D) of different event categories. Signal yields of...

  • Figure6 - Majorana Muon

    Figure 6

    10.17182/hepdata.146757.v1/t7

    Expected and observed upper 95% CL limits on |VNμ|2 as functions of the HNL mass(mN) for a Majorana HNL. For...

  • Figure6 - Dirac muon

    Figure 6

    10.17182/hepdata.146757.v1/t8

    Expected and observed upper 95% CL limits on |VNμ|2 as functions of the HNL mass(mN) for a Dirac HNL. For...

  • Figure6 - Majorana electron

    Figure 6

    10.17182/hepdata.146757.v1/t9

    Expected and observed upper 95% CL limits on |VNe|2 as functions of the HNL mass(mN) for a Majorana HNL. For...

  • Figure6 - Dirac electron

    Figure 6

    10.17182/hepdata.146757.v1/t10

    Expected and observed upper 95% CL limits on |VNe|2 as functions of the HNL mass(mN) for a Dirac HNL. For...

  • Figure6 - Majorana tau

    Figure 6

    10.17182/hepdata.146757.v1/t11

    Expected and observed upper 95% CL limits on |VNtau|2 as functions of the HNL mass(mN) for a Majorana HNL. For...

  • Figure6 - Dirac tau

    Figure 6

    10.17182/hepdata.146757.v1/t12

    Expected and observed upper 95% CL limits on |VNtau|2 as functions of the HNL mass(mN) for a Dirac HNL. For...

  • Figure7 - Majorana 1.5 GeV

    Figure 7

    10.17182/hepdata.146757.v1/t13

    The largest values of the Majorana HNL mass that are excluded at 95% CL are shown as a function of...

  • Figure7 - Dirac 1.5 GeV

    Figure 7

    10.17182/hepdata.146757.v1/t14

    The largest values of the Dirac HNL mass that are excluded at 95% CL are shown as a function of...

  • Figure7 - Majorana ctau 1m

    Figure 7

    10.17182/hepdata.146757.v1/t15

    The largest values of the Majorana HNL mass that are excluded at 95% CL are shown as a function of...

  • Figure7 - Dirac ctau 1m

    Figure 7

    10.17182/hepdata.146757.v1/t16

    The largest values of the Dirac HNL mass that are excluded at 95% CL are shown as a function of...

Loading Data...

Ask a Question


Your question will be emailed to those involved with the submission. Please mention the relevant table.


Please log in to HEPData to send a question.