Improved search for $\nu_\mu \to \nu_e$ oscillation in a long-baseline accelerator experiment

TL;DR

This paper reports an improved search for muon neutrino to electron neutrino oscillations using the K2K experiment, setting new bounds on oscillation parameters with no observed signal.

Contribution

The study provides the most stringent limits to date on $ u_ u o u_e$ oscillations in a long-baseline experiment at the specified $ riangle m^2$ value.

Findings

No evidence for $ u_e$ appearance was observed.

Set an upper limit of $ ext{sin}^2 2 heta_{ u e} < 0.13$ at 90% CL.

Used the full data sample of $9.2 imes 10^{19}$ protons on target.

Abstract

We performed an improved search for $\nu_\mu \to \nu_e$ oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of $9.2 \times 10^{19}$\xspace protons on target. No evidence for a $\nu_e$ appearance signal was found, and we set bounds on the $\nu_\mu \to \nu_e$ oscillation parameters. At $\Delta m^2$ = $2.8 \times 10^{-3} \mathrm{eV}^2$, the best fit value of the K2K $\nu_\mu$ disappearance analysis, we set an upper limit of $\sin^2 2\theta_{\mu e}$ $<$ 0.13 at 90% confidence level.