Sensitivity to the Neutrino Mass Hierarchy

Abstract

In the next decade, a number of experiments will attempt to determine the neutrino mass hierarchy. Feasibility studies for such experiments generally determine the expected value of Delta chi^2. As the hierarchy is a discrete choice, Delta chi^2 does not obey a one degree of freedom chi^2 distribution and so the number of sigmas of confidence of the hierarchy determination is not the square root of the expected Delta chi^2. We present a simple formula for the sensitivity to the hierarchy that can be expected from the median experiment as a function of the expected Delta chi^2.