Dark Side of Higgs Diphoton Decays and Muon g-2
Abstract
We propose that the LHC hints for a Higgs diphoton excess and the muon g-2 (gmu-2) discrepancy between theory and experiment may be related by vector-like "leptons" charged under both U(1)Y hypercharge and a "dark" U(1)d. Quantum loops of such leptons can enhance the Higgs diphoton rate and also generically lead to U(1)Y - U(1)d kinetic mixing. The induced coupling of a light U(1)d gauge boson Zd to electric charge can naturally explain the measured gmu-2. We update Zd mass and coupling constraints based on comparison of the electron g-2 experiment and theory, and find that explaining gmu-2 while satisfying other constraints requires Zd to have a mass ~ 20-100 MeV. We predict new Higgs decay channels gamma Zd and Zd Zd, with rates below the diphoton mode but potentially observable. The boosted Zd -> e+e- in these decays would mimic a promptly converted photon and could provide a fraction of the apparent diphoton excess. More statistics or a closer inspection of extant data may reveal such events.
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