Resolving the LMA-dark NSI degeneracy with coherent neutrino-nucleus scattering

Abstract

In the presence of non-standard neutrino interactions (NSI), a degeneracy exists in neutrino oscillation data, which involves the flipping of the octant of the mixing angle θ12 and the type of the neutrino mass ordering. In this article, we revisit the status of this degeneracy in the light of recent data on coherent elastic neutrino-nucleus scattering (CEνNS) from the COHERENT experiment. For general relative couplings to up and down quarks, the degeneracy is disfavoured at the 2σ level by the latest data but remains at a higher confidence level. We investigate the requirements of future CEνNS measurements to resolve the degeneracy with high significance. We find that a measurement involving both, electron and muon neutrino flavours and a target with a neutron-to-proton ratio close to 1 is required. For example, an experiment with a silicon target at the European Spallation Source can resolve the degeneracy at more than 4σ for arbitrary relative couplings to up and down quarks.

Probing light vector mediators with coherent scattering at future facilities

“…Since the CEνNS cross-section enhancement depends on the mass number of the target nuclei, ideally several of the technologies listed above may be used in order to test with a good precision the SM prediction. This strategy also has the advantage of potentially lifting possible blind spots in the analysis of NP models [15].…”

“…On the other hand, the ESS proposal is interesting because it would allow to increase by approximately one order of magnitude the neutrino flux with respect to the one of the SNS. The ability of such experiments to contribute to the study of CEνNS physics has been studied before [10,11,14,15]. Our purpose here is to extend such studies considering an interesting class of new physics models in which new light spin-1 particles are present.…”

New reactor data improves robustness of neutrino mass ordering determination

“…Constraints on LMA-Dark from scattering experiments only apply if the momentum transfer in the new interaction is larger than the minimal energy measurable by the experiment in question [25,27,70], this puts a lower bound on the mediator mass which can be probed. Previously, COHERENT provided the lowest threshold constraint on the ee part of LMA-Dark down to mediator masses ∼ 50 MeV, for all relevant combinations of d,V ee − u,V ee [27,71], while new data from Dresden-II presented in this paper constrains the ee part of LMA-Dark down to ∼ 1 MeV. Scenarios with lighter mediators are not constrained by scattering.…”

Snowmass White Paper: Beyond the Standard Model effects on Neutrino Flavor

“…[145,[154][155][156]. For example, the combination of oscillations, present COHERENT data and future data obtained using a silicon target at European Spallation Source [157] will be able to discriminate between the standard LMA and LMA-Dark solutions at more than 4 σ C.L., regardless of the relative strength for the NSI couplings to up-and down-type quarks [158].…”