New upper bound of muon neutrino mass in a short-baseline experiment

TL;DR

This paper proposes an improved experimental setup using modern technology and simulations to more accurately measure the muon neutrino mass, achieving a new upper bound of about 150 keV, significantly lower than previous estimates.

Contribution

It introduces a feasible experimental design with reduced uncertainties to set a more precise upper bound on muon neutrino mass using time-of-flight and energy measurements.

Findings

New upper bound of ~150 keV on muon neutrino mass

Reduction of uncertainties compared to previous estimates

Demonstration of feasibility with current technology

Abstract

In the paper Int.J.Mod.Phys.E 23 (2014) 1450004, the potential of short-baseline experiments was proposed to measure the mass (and parameters of Lorentz-violating effects) of the muon neutrino, where a roughly estimated upper bound of 420 eV was given as a possibility with large unknown uncertainties. In the present work, we improve upon this study by focusing on a feasible and improved experimental setup with today's technology, eliminating most large uncertainties, with the use of the Geant4 simulation toolkit. High-energy protons collide with a tungsten target, producing a variety of particles, most importantly pions that decay into muon neutrinos. The detector records the time of flight for both muon and anti-muon neutrinos, utilizing light as a reference signal. Additionally, it captures the energy deposited by neutrinos. By applying the dispersion relation, we determine the muon and/or anti-muon neutrino mass. Our improved results reveal a less optimistic but more accurate and realistic estimated upper bound of the muon neutrino mass, providing a new limit of about 150 keV. Notably, this finding is a factor of three lower than the best upper bound previously established in the literature originating from pion decay in flight.