Abstract
When neutrino masses arise from the exchange of neutral heavy leptons, as in most seesaw schemes, the effective lepton mixing matrix N describing neutrino propagation is non-unitary, hence neutrinos are not exactly orthonormal. New CP violation phases appear in N that could be confused with the standard phase characterizing the three neutrino paradigm. We study the potential of the long-baseline neutrino experiment DUNE in probing CP violation induced by the standard CP phase in the presence of non-unitarity. In order to accomplish this we develop our previous formalism, so as to take into account the neutrino interactions with the medium, important in long baseline experiments such as DUNE. We find that the expected CP sensitivity of DUNE is somewhat degraded with respect to that characterizing the standard unitary case. However the effect is weaker than might have been expected thanks mainly to the wide neutrino beam. We also investigate the sensitivity of DUNE to the parameters characterizing non-unitarity. In this case we find that there is no improvement expected with respect to the current situation, unless the near detector setup is revamped.
Highlights
Following the celebrated discovery of neutrino oscillations [1, 2] subsequent accelerator and reactor studies have brought neutrino physics to the mature phase of precision studies
Sensitive laboratory oscillation studies play a key role in confirming the neutrino oscillation hypothesis, and rule out exotic solutions, establishing the robustness of the simplest three neutrino paradigm
These issues have been widely explored, so here we focus on the impact of non-unitarity of the lepton mixing matrix upon neutrino propagation and the resulting expected sensitivities on the three–neutrino CP phase determination [29,30,31]
Summary
Following the celebrated discovery of neutrino oscillations [1, 2] subsequent accelerator and reactor studies have brought neutrino physics to the mature phase of precision studies. More than ever it has become relevant to critically assess with improved sensitivity the robustness of the determination of the three-neutrino oscillation parameters within recent and current studies [3,4,5,6,7,8,9,10] as well as future experiments [11] This includes the scrutiny of the uncertainties associated with neutrino fluxes, propagation and interactions. On the other hand the subleading role of neutrino non-standard interactions upon oscillations has been considered in various contexts and can bring new sources of CP violation [24,25,26,27,28] These issues have been widely explored, so here we focus on the impact of non-unitarity of the lepton mixing matrix upon neutrino propagation and the resulting expected sensitivities on the three–neutrino CP phase determination [29,30,31].
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