More ingredients for an Altarelli cocktail at MiniBooNE

The MiniBooNE excess persists as a significant puzzle in particle physics. Given that the MiniBooNE detector cannot discriminate between electron-like signals and backgrounds due to photons, the goal of this work is to study photon backgrounds in MiniBooNE in depth. We first consider a novel single-photon background arising from multi-nucleon scattering with coherently enhanced initial or final state radiation. This class of processes, which we dub 2p2h gamma (two-particle-two-hole + photon) can explain similar to 40 of the similar to 560 excess events observed by MiniBooNE in neutrino mode. Second, we consider the background from neutral-current single-pi(0) production, where two photons from pi(0) -> gamma gamma decay are mis-identified as an electron-like shower. We construct a phenomenological likelihood that reproduces MiniBooNE's pi(0) -> gamma gamma background faithfully. Even with data-driven background estimation techniques, we find there is a residual dependence on the Monte Carlo generator used. Our results motivate a reduction in the significance of the MiniBooNE excess by 0.4 sigma.

Automated summary

The study focuses on understanding photon backgrounds in the MiniBooNE detector, which cannot distinguish between electron-like signals and photon backgrounds. Two sources of backgrounds are explored: the 2p2h gamma process which can explain a significant portion of the excess events observed, and the mis-identification of photons from pi(0) -> gamma gamma decay as an electron-like shower. The results suggest a reduction in the significance of the MiniBooNE excess by 0.4 sigma.