A Study of Muon Neutrino Disappearance Using the Fermilab Main Injector Neutrino Beam

TL;DR

This paper reports a significant muon-neutrino disappearance observed over 734 km, consistent with neutrino oscillations, based on data collected at Fermilab with two detectors and a large exposure of protons on target.

Contribution

First measurement of muon-neutrino disappearance over 734 km using the Fermilab Main Injector beam with two detectors, providing evidence for neutrino oscillations.

Findings

Observed 215 muon-neutrino interactions vs. 336 expected without oscillations.

Detected a 5.2 sigma deficit indicating neutrino oscillations.

Measured oscillation parameters: delta m^2 = 2.74e-3 eV^2, sin^2(2θ) > 0.87.

Abstract

We report the results of a search for muon-neutrino disappearance by the Main Injector Neutrino Oscillation Search. The experiment uses two detectors separated by 734 km to observe a beam of neutrinos created by the Neutrinos at the Main Injector facility at Fermi National Accelerator Laboratory. The data were collected in the first 282 days of beam operations and correspond to an exposure of 1.27e20 protons on target. Based on measurements in the Near Detector, in the absence of neutrino oscillations we expected 336 +/- 14 muon-neutrino charged-current interactions at the Far Detector but observed 215. This deficit of events corresponds to a significance of 5.2 standard deviations. The deficit is energy dependent and is consistent with two-flavor neutrino oscillations according to delta m-squared = 2.74e-3 +0.44/-0.26e-3 eV^2 and sin^2(2 theta) > 0.87 at 68% confidence level.