Resolving the mass hierarchy with atmospheric neutrinos using a liquid argon detector

Abstract

We explore the potential offered by large-mass liquid argon detectors for determination of the sign of Δm²₃₁ or the neutrino mass hierarchy, through interactions of atmospheric neutrinos. We give results for a 100 kT sized magnetized detector which provides separate sensitivity to ν_μ, ν_μand over a limited energy range, to ν_e, ν_e. We also discuss the sensitivity for the unmagnetized version of such a detector. After including the effect of smearing in neutrino energy and direction and incorporating the relevant statistical, theoretical, and systematic errors, we perform a binned χ² analysis of simulated data. The ν² is marginalized over the presently allowed ranges of neutrino parameters and determined as a function of θ₁₃. We find that such a detector offers superior capabilities for hierarchy resolution, allowing a >4σ determination for a 100 kT detector over a 10-year running period for values of sin ²2θ₁₃ ≥ 0.05. For an unmagnetized detector, a 2.5σ hierarchy sensitivity is possible for sin ²2θ₁₃ = 0.04.