Enhanced search for neutral current Δ radiative single-photon production in MicroBooNE
We report results from an updated search for neutral current (NC) resonant Δ(1232) baryon production and subsequent Δ radiative decay (NC Δ → 𝑁𝛾). We consider events with and without final state protons; events with a proton can be compared with the kinematics of a Δ(1232) baryon decay, while events without a visible proton represent a more generic phase space. In order to maximize sensitivity to each topology, we simultaneously make use of two different reconstruction paradigms, Pandora and Wire-Cell, which have complementary strengths, and select mostly orthogonal sets of events. Considering an overall scaling of the NC Δ → 𝑁𝛾 rate as an explanation of the MiniBooNE anomaly, our data exclude this hypothesis at 94.4% CL. When we decouple the expected correlations between NC Δ → 𝑁𝛾 events with and without final state protons, our data exclude an interpretation in which all excess events have associated protons at 2.0𝜎, and are consistent with an interpretation in which all excess events have no associated protons at 0.63𝜎.