Latest Results of the KARMEN2 Experiment

TL;DR

The KARMEN2 experiment analyzed neutrino oscillation data from 1997-2000, found no evidence of oscillations, and set new upper limits on the oscillation parameters, refuting previous anomalies observed in earlier data.

Contribution

This study provides updated experimental limits on neutrino oscillation parameters, improving constraints and clarifying previous anomalies with a larger data set.

Findings

No excess events indicating oscillations were observed.

Set upper limit on sin^2(2θ) < 1.3×10^-3 at 90% confidence.

Confirmed absence of the earlier observed anomaly in KARMEN1 data.

Abstract

The neutrino experiment KARMEN at the beam stop neutrino source ISIS investigates the oscillation channel numubar->nuebar in the appearance mode by looking for p(nuebar,e+)n reactions. An analysis of data collected from February 1997 through March 2000 with the KARMEN2 experimental setup reveals 11 candidate events in good agreement with the background expectation of 12.3+-0.6 events. Hence, there is no indication of an oscillation signal. A maximum likelihood analysis of the data leads to an upper limit (at 90% confidence level) for the mixing angle of sin^2(2theta) < 1.3x10^-3 at large Dm^2 and Dm^2 < 0.049 eV^2 for sin^2(2theta)=1. The anomaly in the time spectrum of events induced by nue and numubar seen in the KARMEN1 data could not be confirmed with the KARMEN2 data.