Searching for Flavor-Violating ALPs in Higgs Decays

Abstract

Pseudo-scalar particles, often referred to as axion-like-particles (ALPs), arise in a variety of theoretical contexts. The phenomenology of such states is typically studied assuming flavor-conserving interactions, yet they can in principle have flavor-violating (FV) couplings to fermions. We consider this general possibility, focusing on models where the ALP has non-negligible coupling to the Standard Model Higgs boson $h$. For a lepton FV ALP $a$ of mass $m_a\gtrsim 2$ GeV, $a\to \tau \ell$, where $\ell \ne \tau$ is a charged lepton, could have $\mathcal{O}(1)$ branching fraction, leading to potentially detectable $h\to aa\to \tau \ell \tau \ell$ at the LHC and its future program. We examine this possibility, in light of existing bounds on FV processes, in a general effective theory. We obtain constraints on the effective couplings from both prompt and long-lifetime searches at the LHC; some projections for envisioned measurements are also provided. The implications of the recently announced first results of the muon $g-2$ measurement at Fermilab for the ALP interactions considered in our work are also briefly discussed.

26 pages, 10 figures. v2: updated to published version

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Cited by in corpus (9)

• Lepton-Flavor-Violating ALPs at the Electron-Ion Collider: A Golden Opportunity
• Searching for the axion-like particle at the EIC
• Exotic Higgs Decays
• Lepton-Flavor-Violating ALP Signals with TeV-Scale Muon Beams
• The Muon Magnetic Moment and Physics Beyond the Standard Model
• Flavor-Violating ALPs, Electron g-2, and the Electron-Ion Collider
• Light Axion-Like Particles at Future Lepton Colliders
• Flavor-changing light bosons with accidental longevity
• Electron Beam Dump Constraints on Light Bosons with Lepton Flavor Violating Couplings