Detection of Accelerator-Produced Neutrinos at a Distance of 250 km

TL;DR

This paper reports the detection of neutrinos produced by an accelerator at a distance of 250 km, providing evidence for neutrino oscillations through observed event rates compared to expectations.

Contribution

It presents the first detection of accelerator-produced neutrinos at a long baseline of 250 km, supporting neutrino oscillation hypotheses with experimental data.

Findings

28 neutrino events detected versus 37.8 expected

Background noise is negligible (~10^-3 events)

Supports neutrino oscillation hypothesis

Abstract

The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time of the beam in the 22.5 kt fiducial volume of Super--Kamiokande, the far detector at 250 km distance. The expectation is 37.8+3.5-3.8, derived using measurements of neutrino interactions in a near detector and extrapolation using a beam simulation validated by a measurement of pion kinematics after production and focusing. The background is of order 10^-3 events.