2025/11/24 by CMS Collaboration · 2 voices
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)
paper · doi:10.48550/arxiv.2511.19563
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 √(s) = 13 TeV, collected with the CMS detector in 2016-2018 and corresponding to an integrated luminosity of 138 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 → AA → 4e are set at 95% confidence level, for masses between 10 and 100 MeV and proper decay lengths below 100 μm, 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.