Search for light pseudoscalar bosons, pair-produced in Higgs boson decays in the four-electron final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration
CMS-EXO-24-031, 2025.

Abstract (data abstract)
A search for pairs of light neutral pseudoscalar bosons ($ A$) resulting from the decay of a Higgs boson is performed. The search is conducted using LHC proton-proton collision data at $\sqrt{s} = 13~\mathrm{TeV}$, collected with the CMS detector in 2016--2018 and corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$. The $ A$ boson decays into a highly collimated electron-positron pair. A novel multivariate algorithm using tracks and calorimeter information is developed to identify these distinctive signatures, and events are selected with two such merged electron-positron pairs. No significant excess above the standard model background predictions is observed. Upper limits on the branching fraction for $ H\to A A\to4 e$ are set at $95\%$ confidence level, for masses between 10 and 100 MeV and proper decay lengths below 100 $\mu\mathrm{m}$ ; reaching branching fraction sensitivities as low as $10^{-5}$. This is the first search for Higgs boson decays to four electrons via light pseudoscalars at the LHC. It significantly improves the experimental sensitivity to axion-like particles with masses below 100 MeV.

  • Figure 1

    Data from Figure 1.

    10.17182/hepdata.159276.v1/t1

    Invariant mass distribution of the four-electron system ($m_{4 e}$) for selected events (points), compared to the background-only fit (red) with...

  • Figure 2

    Data from Figure 2.

    10.17182/hepdata.159276.v1/t2

    Observed (solid points) and expected (dashed lines) $95\%$ CL upper limits on the Higgs boson branching fraction to a pair...

  • Figure 3

    Data from Figure 3.

    10.17182/hepdata.159276.v1/t3

    A map of the observed $95\%$ CL upper limit on the Higgs boson branching fraction for $ H \to A...

  • Additional Table 1 (2016preVFP Barrel object level Cutflow)

    Supplementary Table I (barrel object-level)

    10.17182/hepdata.159276.v1/t4

    Selection efficiencies for the barrel region at object level. Definitions used in this table: Track-Match efficiency (barrel / endcap) is...

  • Additional Table 1 (2016preVFP endcap object level Cutflow)

    Supplementary Table I (endcap object-level)

    10.17182/hepdata.159276.v1/t5

    Selection efficiencies for the endcap region at object level. Definitions as above.

  • Additional Table 1 (2016preVFP event level Cutflow)

    Supplementary Table I (event level)

    10.17182/hepdata.159276.v1/t6

    Trigger-level and overall event-level efficiency.Definitions used in this table: Trigger efficiency is defined as the number of events passing both...

  • Additional Table 2 (2016postVFP Barrel object level Cutflow)

    Supplementary Table II (barrel object-level)

    10.17182/hepdata.159276.v1/t7

    Selection efficiencies for the barrel region at object level. Definitions used in this table: Track-Match efficiency (barrel / endcap) is...

  • Additional Table 2 (2016postVFP Endcap object level Cutflow)

    Supplementary Table II (endcap object-level)

    10.17182/hepdata.159276.v1/t8

    Selection efficiencies for the endcap region at object level. Definitions as above.

  • Additional Table 2 (2016postVFP event level Cutflow)

    Supplementary Table II (event level)

    10.17182/hepdata.159276.v1/t9

    Trigger-level and overall event-level efficiency.Definitions used in this table: Trigger efficiency is defined as the number of events passing both...

  • Additional Table 3 (2017 Barrel object level Cutflow)

    Supplementary Table III (barrel object-level)

    10.17182/hepdata.159276.v1/t10

    Selection efficiencies for the barrel region at object level. Definitions used in this table: Track-Match efficiency (barrel / endcap) is...

  • Additional Table 3 (2017 Endcap object level Cutflow)

    Supplementary Table III (endcap object-level)

    10.17182/hepdata.159276.v1/t11

    Selection efficiencies for the endcap region at object level. Definitions as above.

  • Additional Table 3 (2017 event level Cutflow)

    Supplementary Table III (event level)

    10.17182/hepdata.159276.v1/t12

    Trigger-level and overall event-level efficiency.Definitions used in this table: Trigger efficiency is defined as the number of events passing both...

  • Additional Table 4 (2018 Barrel object level Cutflow)

    Supplementary Table IV (barrel object-level)

    10.17182/hepdata.159276.v1/t13

    Selection efficiencies for the barrel region at object level. Definitions used in this table: Track-Match efficiency (barrel / endcap) is...

  • Additional Table 4 (2018 Endcap object level Cutflow)

    Supplementary Table IV (endcap object-level)

    10.17182/hepdata.159276.v1/t14

    Selection efficiencies for the endcap region at object level. Definitions as above.

  • Additional Table 4 (2018 event level Cutflow)

    Supplementary Table IV (event level)

    10.17182/hepdata.159276.v1/t15

    Trigger-level and overall event-level efficiency.Definitions used in this table: Trigger efficiency is defined as the number of events passing both...

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.