Searching for a leptophobic B boson through η → π0γγ and ηʹ → π0γγ decays

Abstract

The sensitivity of the decays η → π0γγ and ηʹ → π0γγ to a leptophobic B boson in the sub-GeV mass range is summarised in this work. By adding an explicit B-boson resonance exchange to the dominant Standard Model contribution from vector meson exchanges, and employing experimental measurements of the associated branching ratios, the current constraints on the B-boson mass mB and coupling to Standard Model particles αB are significantly improved. From these constraints and the analysis of the available experimental γγ invariant mass distribution of η → π0γγ, we conclude that a B-boson signature in the resonant mass range mπ0 ≲ mB ≲ mη is strongly suppressed and would be very difficult to experimentally identified. The η΄ → π0γγ decay is not as powerful as the η → π0γγ at constraining B-boson parameters below mη but allow exploring larger B-boson masses. Yet, the task of identifying a B-boson with mB ∼ mω would be very challenging.