A study of invisible neutrino decay at DUNE and its effects on θ 23 measurement

Abstract

We study the consequences of invisible decay of neutrinos in the context of the DUNE experiment. We assume that the third mass eigenstate is unstable and decays to a light sterile neutrino and a scalar or a pseudo-scalar. We consider DUNE running in 5 years neutrino and 5 years antineutrino mode and a detector volume of 40 kt. We obtain the expected sensitivity on the rest-frame life-time τ₃ normalized to the mass m₃ as τ₃/m₃> 4.50 × 10⁻¹¹ s/eV at 90% C.L. for a normal hierarchical mass spectrum. We also find that DUNE can discover neutrino decay for τ₃/m₃> 4.27 × 10⁻¹¹ s/eV at 90% C.L. In addition, for an unstable ν₃ with an illustrative value of τ₃/m₃ = 1.2 × 10⁻¹¹ s/eV, the no decay case could get disfavoured at the 3σ C.L. At 90% C.L. the expected precision range for this true value is obtained as 1.71 × 10⁻¹¹> τ₃/m₃> 9.29 × 10⁻¹² in units of s/eV. We also study the correlation between a non-zero τ₃/m₃ and standard oscillation parameters and find an interesting correlation in the appearance and disappearance channels with the mixing angle θ₂₃. This alters the octant sensitivity of DUNE, favorably (unfavorably) for true θ₂₃ in the lower (higher) octant. The effect of a decaying neutrino does not alter the hierarchy or CP violation discovery sensitivity of DUNE in a discernible way.