Upper limits for neutrino oscillations muon-antineutrino to electron-antineutrino from muon decay at rest

TL;DR

The KARMEN experiment searched for muon-antineutrino to electron-antineutrino oscillations using decay-at-rest neutrinos, found no evidence, and set new upper limits on oscillation parameters, challenging previous claims by LSND.

Contribution

This study provides new upper limits on neutrino oscillation parameters, significantly constraining the parameter space suggested by earlier experiments.

Findings

No evidence for ueb appearance in the data.

Set upper limits: sin^2(2theta)<1.7x10^-3 for Dm^2>100 eV^2.

Excluded the favored parameter region of LSND.

Abstract

The KARMEN experiment at the spallation neutron source ISIS used \numub from \mup--decay at rest in the search for neutrino oscillations \numubnueb in the appearance mode, with p(\nueb,e+)n as detection reaction of \nueb. In total, 15 candidates fulfill all conditions for the \nueb signature, in agreement with the background expectation of 15.8+-0.5 events, yielding no indication for oscillations. A single event based likelihood analysis leads to upper limits on the oscillation parameters: sin^2(2theta)<1.7x10e-3 for Dm^2>100 eV^2 and Dm^2<0.055 eV^2 for sin^2(2theta)=1 at 90% confidence. Thus, KARMEN does not confirm the LSND experiment and restricts significantly its favored parameter region for \numubnueb.