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

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.