Abstract
We show that neutral current (NC) measurements at neutrino detectors can play a valuable role in the search for new physics. Such measurements have certain intrinsic features and advantages that can fruitfully be combined with the usual well-studied charged lepton detection channels in order to probe the presence of new interactions or new light states. In addition to the fact that NC events are immune to uncertainties in standard model neutrino mixing and mass parameters, they can have small matter effects and superior rates since all three flavours participate. We also show, as a general feature, that NC measurements provide access to different combinations of CP phases and mixing parameters compared to CC measurements at both long and short baseline experiments. Using the Deep Underground Neutrino Experiment (DUNE) as an illustrative setting, we demonstrate the capability of NC measurements to break degeneracies arising in CC measurements, allowing us, in principle, to distinguish between new physics that violates three flavour unitarity and that which does not. Finally, we show that NC measurements can enable us to restrict new physics parameters that are not easily constrained by CC measurements.
Highlights
Neutral current and new physics at long baselinesFor the remainder of this paper, we focus largely, but not exclusively, on the 3+1 scenario in order to study the potential of neutral current (NC) events as a probe and diagnostic tool for new physics
The final state, and neutrino coherent pion scattering.1 Similar processes exist, for anti-neutrinos
We show that neutral current (NC) measurements at neutrino detectors can play a valuable role in the search for new physics
Summary
For the remainder of this paper, we focus largely, but not exclusively, on the 3+1 scenario in order to study the potential of NC events as a probe and diagnostic tool for new physics. It should be noted that the backgrounds too, will oscillate into the sterile flavour depending on the values of Ue4, Uμ4 and Uτ4 In such a scenario, the simplifying assumptions of putting one or more of these matrix elements to 0, may not give the correct estimate of the NC signal events. We note that in the 3+1 scenario, flavor oscillations may lead to some depletion of the active neutrino flux and of its muon neutrino component at the location of the DUNE near detector (∼ 500 m). This could, in principle, distort the flux measurement made at this location, which forms the basis of conclusions drawn regarding oscillations measured at the far detector. As we show in this work, depletion in the NC rate significantly above this uncertainty is expected at the far detector, enabling DUNE to detect the possible presence of a sterile state via neutral current measurements
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