Abstract
Experimental tests of Lorentz symmetry in systems of all types are critical for ensuring that the basic assumptions of physics are well-founded. Data from all phases of the Sudbury Neutrino Observatory, a kiloton-scale heavy water Cherenkov detector, are analyzed for possible violations of Lorentz symmetry in the neutrino sector. Such violations would appear as one of eight possible signal types in the detector: six seasonal variations in the solar electron neutrino survival probability differing in energy and time dependence, and two shape changes to the oscillated solar neutrino energy spectrum. No evidence for such signals is observed, and limits on the size of such effects are established in the framework of the Standard Model Extension, including 40 limits on perviously unconstrained operators and improved limits on 15 additional operators. This makes limits on all minimal, Dirac-type Lorentz violating operators in the neutrino sector available for the first time.
Highlights
Solar neutrinos are produced in the electron flavor
If Lorentz symmetry is slightly broken in the neutrino sector, one would expect that neutrinos propagating in different directions would behave slightly differently
Vacuum oscillation effects come to dominate as the neutrino escapes the Sun, but since the neutrino energy cannot be resolved on a scale at all comparable to the number of oscillation lengths traveled from the Sun, these oscillations are averaged over
Summary
Solar neutrinos are produced in the electron flavor. At the relevant energies, the electron flavor fraction of the active solar neutrino flux after it has propagated to the Earth is roughly 1=3. If Lorentz symmetry is slightly broken in the neutrino sector, one would expect that neutrinos propagating in different directions would behave slightly differently. This could result in a change in the electron neutrino survival probability as a function of direction of propagation. Over the course of a year, the propagation direction of solar neutrinos detected at SNO rotated through a full circle, following the Earth in the frame of the Sun. SNO was sensitive to such Lorentz violations as a time-of-year variation in the electron neutrino survival probability.
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