Search for an anomalous excess of inclusive charged-current $\hat{I}{½}_e$ interactions in the MicroBooNE experiment using Wire-Cell reconstruction

Abstract

We report a search for an anomalous excess of inclusive charged-current (CC) $\hat{I}{½}_e$ interactions using the Wire-Cell event reconstruction package in the MicroBooNE experiment, which is motivated by the previous observation of a low-energy excess (LEE) of electromagnetic events from the MiniBooNE experiment. With a single liquid argon time projection chamber detector, the measurements of $\hat{I}{½}_{\hat{I}}¼$ CC interactions as well as $\ddot{I}{€}^0$ interactions are used to constrain signal and background predictions of $\hat{I}{½}_e$ CC interactions. A data set collected from February 2016 to July 2018 corresponding to an exposure of 6.369 $\times$ 10${}^{20}$ protons on target from the Booster Neutrino Beam at FNAL is analyzed. With $x$ representing an overall normalization factor and referred to as the LEE strength parameter, we select 56 fully contained $\hat{I}{½}_e$ CC candidates while expecting 69.6 $\pm$ 8.0 (stat.) $\pm$ 5.0 (sys.) and 103.8 $\pm$ 9.0 (stat.) $\pm$ 7.4 (sys.) candidates after constraints for the absence (eLEE${}_{x=0}$) of the median signal strength derived from the MiniBooNE observation and the presence (eLEE${}_{x=1}$) of that signal strength, respectively. Under a nested hypothesis test using both rate and shape information in all available channels, the best-fit $x$ is determined to be 0 (eLEE${}_{x=0}$) with a 95.5% confidence level upper limit of $x$ at 0.502. Under a simple-vs-simple hypotheses test, the eLEE${}_{x=1}$ hypothesis is rejected at 3.75$\ddot{I}ƒ$, while the eLEE${}_{x=0}$ hypothesis is shown to be consistent with the observation at 0.45$\ddot{I}ƒ$. In the context of the eLEE model, the estimated 68.3% confidence interval of the $\hat{I}{½}_e$ hypothesis to explain the LEE observed in the MiniBooNE experiment is disfavored at a significance level of more than 2.6$\ddot{I}ƒ$ (3.0$\ddot{I}ƒ$) considering MiniBooNE's full (statistical) uncertainties.

40 pages, 32 figures, 6 tables