2025/03/11 by Cepeda, M., No, J. M., Ramos, C. +2 · 1 citation
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2503.08781
Exotic Higgs decays are among the most promising areas to be explored at the High-Luminosity LHC, given the unprecedentedly large amount (∼ 3 × 108) of 125 GeV Higgs bosons that will be produced. In this context, we propose a new search channel for which the Higgs boson decays to a (leptonically decaying) Z boson and a light BSM pseudoscalar a, which subsequently decays to a pair of τ-leptons (h → Z a → ℓℓ ττ). After performing a validation of existing ATLAS and CMS exotic Higgs decay searches in related channels, we analyze the HL-LHC projected sensitivity of our a→ ττ search, targeting the kinematic region where the exotic Higgs decay is two-body. We are able to probe pseudoscalar masses ma ∈ [5, 33] GeV by leveraging both leptonic and hadronic τ decays, and establish model-independent 95% C.L. sensitivity projections on the branching fraction \rm BR(h → Z a) × \rm BR(a → ττ). These a→ ττ projections yield a competitive probe of light pseudoscalars, which depending on the model can become significantly more sensitive than projections from existing experimental searches in a → μμ and a → γγ final states. Finally, we explore the potential of our search to probe an Axion-Like-Particle (ALP) solution to the muon (g-2) anomaly (when taken face-value), finding that our proposed h→ Z a, a→ττ search can provide valuable constraints on such ALP scenario, in complementarity with existing h→ Z a, a → γγ experimental searches.