Upper bound on neutrino mass based on T2K neutrino timing measurements

TL;DR

This paper uses timing measurements from the T2K neutrino experiment to set an upper bound on neutrino mass, achieving sensitivity in the few MeV/c^2 range by analyzing neutrino time of flight and energy correlations.

Contribution

It introduces a novel method of constraining neutrino mass using timing data from T2K, providing the first upper limit based on this approach.

Findings

90% confidence level upper limit on neutrino mass squared: 5.6 MeV^2/c^4

Timing measurements can probe neutrino masses in the few MeV/c^2 range

Neutrino time of flight analysis constrains neutrino mass eigenstates

Abstract

The Tokai to Kamioka (T2K) long-baseline neutrino experiment consists of a muon neutrino beam, produced at the J-PARC accelerator, a near detector complex and a large 295km distant far detector. The present work utilizes the T2K event timing measurements at the near and far detectors to study neutrino time of flight as function of derived neutrino energy. Under the assumption of a relativistic relation between energy and time of flight, constraints on the neutrino rest mass can be derived. The sub-GeV neutrino beam in conjunction with timing precision of order tens of ns provide sensitivity to neutrino mass in the few MeV/$c^2$ range. We study the distribution of relative arrival times of muon and electron neutrino candidate events at the T2K far detector as a function of neutrino energy. The 90% C.L. upper limit on the mixture of neutrino mass eigenstates represented in the data sample is found to be m$_{\nu}^2 < 5.6 \, {\mathrm MeV^2/}c^4$.