Abstract
We revisit neutrino oscillations in matter considering the open quantum system framework, which allows to introduce possible decoherence effects generated by New Physics in a phenomenological manner. We assume that the decoherence parameters gamma _{ij} may depend on the neutrino energy, as gamma _{ij}=gamma _{ij}^{0}(E/text {GeV})^n (n = 0,pm 1,pm 2) . The case of non-uniform matter is studied in detail and, in particular, we develop a consistent formalism to study the non-adiabatic case dividing the matter profile into an arbitrary number of layers of constant densities. This formalism is then applied to explore the sensitivity of IceCube and DeepCore to this type of effects. Our study is the first atmospheric neutrino analysis where a consistent treatment of the matter effects in the three-neutrino case is performed in presence of decoherence. We show that matter effects are indeed extremely relevant in this context. We find that IceCube is able to considerably improve over current bounds in the solar sector (gamma _{21}) and in the atmospheric sector (gamma _{31} and gamma _{32}) for n=0,1,2 and, in particular, by several orders of magnitude (between 3 and 9) for the n=1,2 cases. For n=0 we find gamma _{32},gamma _{31}< 4.0times 10^{-24}, (1.3times 10^{-24}) hbox {GeV} and gamma _{21}<1.3times 10^{-24}, (4.1times 10^{-24}) hbox {GeV} at the 95% CL, for normal (inverted) mass ordering.
Highlights
The accurate measurement of the mixing angle θ13 by reactor neutrino experiments [1], with a small uncertainty comparable to that for θ12, has initiated a precision era for neutrino physics
A global fit to neutrino oscillation data seems to show a mild preference for a normal mass ordering, which needs to be confirmed as more data become available
We will show that it strongly depends on the neutrino mass ordering and on whether the sensitivity is dominated by the neutrino or antineutrino channels: for neutrinos the decoherence effects at high energies are mainly driven by γ21 (γ31) for normal ordering, while in the antineutrino channel they are essentially controlled by γ32 (γ21) for normal ordering
Summary
The accurate measurement of the mixing angle θ13 by reactor neutrino experiments [1], with a small uncertainty comparable to that for θ12, has initiated a precision era for neutrino physics. 614 Page 2 of 18 the Super-Kamiokande (SK) experiment [25–28] They considered the general case in which the decoherence parameters could depend on the neutrino energy via a power law, γ = γ0(E/GeV)n, where n = 0, −1, 2. In [17] it was shown that the ∼ 2σ tension between T2K and NOvA on the measurement of the atmospheric mixing angle θ23 could be alleviated through the inclusion of decoherence effects in the atmospheric neutrino sector, namely, γ23 = (2.3±1.1)×10−23 GeV Such value of γ23 would be close to the SK bound from Ref. Several analyses of decoherence effects on present and future long-baseline neutrino oscillation experiments have been recently performed (albeit at the probability level only), see e.g. Refs. Appendices A and B discuss technical details regarding some of the approximations used in our numerical calculations
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