HET Lunch Discussion

"Revisiting the Dark Photon Interpretation of the Muon Anomalous Magnetic Moment"

Presented by Gopi Mohlabeng, BNL

Friday, July 26, 2019, 12:15 pm — Building 510, Room 2-160

A massive U(1)′ gauge boson known as a "dark photon" or A′, has long been proposed as a potential explanation for the discrepancy observed between the experimental measurement and theoretical determination of the anomalous magnetic moment of the muon (gμ − 2) anomaly. Recently, experimental results have excluded this possibility for a dark photon exhibiting exclusively visible or invisible decays. In this work, we revisit this idea and consider a model where A′ couples inelastically to dark matter and an excited dark sector state, leading to a more exotic decay topology we refer to as a semi-visible decay. We show that for large mass splittings between the dark sector states this decay mode is enhanced, weakening the previous invisibly decaying dark photon bounds. As a consequence, A′ resolves the gμ− 2 anomaly in a region of parameter space the thermal dark matter component of the Universe is readily explained. Interestingly, it is possible that the semi-visible events we discuss may have been vetoed by experiments searching for invisible dark photon decays. A re-analysis of the data and future searches may be crucial in uncovering this exotic decay mode or closing the window on the dark photon explanation of the gμ− 2 anomaly.

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