Dark Side of Higgs Diphoton Decays and Muon g-2

TL;DR

This paper explores a unified explanation for the Higgs diphoton excess and muon g-2 anomaly through vector-like leptons and a light dark gauge boson, predicting new Higgs decay channels and potential observable signals.

Contribution

It proposes a model linking Higgs diphoton excess and muon g-2 via vector-like leptons and a light dark gauge boson, with updated constraints and novel decay predictions.

Findings

Light dark gauge boson Z_d with mass ~20-100 MeV can explain muon g-2.

Predicted Higgs decays include gamma Z_d and Z_d Z_d channels.

Boosted Z_d -> e+e- could mimic photon signals, affecting diphoton excess interpretation.

Abstract

We propose that the LHC hints for a Higgs diphoton excess and the muon g-2 (g_mu-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 Z_d to electric charge can naturally explain the measured g_mu-2. We update Z_d mass and coupling constraints based on comparison of the electron g-2 experiment and theory, and find that explaining g_mu-2 while satisfying other constraints requires Z_d to have a mass ~ 20-100 MeV. We predict new Higgs decay channels gamma Z_d and Z_d Z_d, with rates below the diphoton mode but potentially observable. The boosted Z_d -> 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.