First Observation of Coherent $\pi^0$ Production in Neutrino Nucleus Interactions with $E_{\nu}<$ 2 GeV

TL;DR

This paper reports the first observation of coherent neutral current $b0$ production in neutrino-nucleus interactions below 2 GeV, providing crucial data on a background for neutrino oscillation experiments.

Contribution

It presents the first measurement of coherent $b0$ production at low energies and quantifies its contribution to neutral current $b0$ production in neutrino interactions.

Findings

Coherent $b0$ production accounts for about 19.5% of all neutral current $b0$ production.

First observation of coherent $b0$ production below 2 GeV.

Measurement helps refine background estimates for neutrino oscillation searches.

Abstract

The MiniBooNE experiment at Fermilab has amassed the largest sample to date of $\pi^0$s produced in neutral current (NC) neutrino-nucleus interactions at low energy. This paper reports a measurement of the momentum distribution of $\pi^0$s produced in mineral oil (CH$_2$) and the first observation of coherent $\pi^0$ production below 2 GeV. In the forward direction, the yield of events observed above the expectation for resonant production is attributed primarily to coherent production off carbon, but may also include a small contribution from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino flux, the sum of the NC coherent and diffractive modes is found to be (19.5 $\pm$1.1 (stat) $\pm$2.5 (sys))% of all exclusive NC $\pi^0$ production at MiniBooNE. These measurements are of immediate utility because they quantify an important background to MiniBooNE's search for $\nu_{\mu} \to \nu_e$ oscillations.