Ge, S. F., Pasquini, P., Tortola, M., & Valle, J. W. F. (2017). Measuring the leptonic CP phase in neutrino oscillations with nonunitary mixing. Phys. Rev. D, 95(3), 033005–14pp.
Abstract: Non-unitary neutrino mixing implies an extra CP violating phase that can fake the leptonic Dirac CP phase delta(CP) of the simplest three-neutrino mixing benchmark scheme. This would hinder the possibility of probing for CP violation in accelerator-type experiments. We take T2K and T2HK as examples to demonstrate the degeneracy between the “standard” (or “unitary”) and “nonunitary” CP phases. We find, under the assumption of nonunitary mixing, that their CP sensitivities severely deteriorate. Fortunately, the TNT2K proposal of supplementing T2(H)K with a μDAR source for better measurement of delta(CP) can partially break the CP degeneracy by probing both cos delta(CP) and sin delta(CP) dependences in the wide spectrum of the μDAR flux. We also show that the further addition of a near detector to the μDAR setup can eliminate the degeneracy completely.
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Pasquini, P. S., & Peres, O. L. G. (2016). Bounds on neutrino-scalar Yukawa coupling. Phys. Rev. D, 93(5), 053007–8pp.
Abstract: General neutrino-scalar couplings appear in many extensions of the Standard Model. We can probe these neutrino-scalar couplings by a leptonic decay of mesons and from a heavy neutrino search. Our analysis improves the present limits to vertical bar g(e)vertical bar(2) < 1.9 x 10(-6) and vertical bar g(mu)vertical bar(2) < 1.9 x 10(-7) at 90% C.L. for massless scalars. For massive scalars, we found for the first time the constraints for g(alpha)(2) couplings to be 10(-6) – 10(-1), respectively, for scalar masses between up 100 MeV, and we have no limits for masses above 300 MeV.
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