A study of invisible neutrino decay at DUNE and its effects on θ₂₃ 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 bounds 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 gets disfavoured at the 3σ C.L. At 90\% C.L. the allowed range for this true value is obtained as 1.71×10_-11>τ₃/m₃>9.29×10_-12in 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 channel probability with the mixing angle θ23. This alters the octant sensitvity 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 discovery sensitivity of DUNE in a discernible way.