Why Is The Neutrino Oscillation Formula Expanded In Δm212/Δm312\Delta m_{21}^{2}/\Delta m_{31}^{2} Still Accurate Near The Solar Resonance In Matter?

The conventional approximate formula for neutrino oscillation in matter which is obtained from the expansion in terms of the ratio of mass square differences $\alpha=\Delta m_{21}^{2}/\Delta m_{31}^{2}\approx0.03$, first proposed by Cervera, et al and Freund, turns out to be an accurate formula for accelerator neutrino experiments. Originally it required the neutrino energy to be well above the solar resonance to validate the expansion but it is found to be still very accurate when the formula is extrapolated to the resonance, which is practically important for the T2K experiment. This paper shows that the accuracy is guaranteed by cancellations of branch cut singularities and also, for the first time, analytically computes the actual error of the formula. The actual error implies that the original requirement can be safely removed in current experiments.Comment: 22 pages,7 figures. Some materials are removed for simplicity. Accepted by JHE

Tensor and scalar interactions of neutrinos may lead to observable neutrino magnetic moments

Recently more generalized four-fermion interactions of neutrinos such as tensor and scalar interactions (TSIs) have been extensively studied in response to forthcoming precision measurements of neutrino interactions. In this letter, we show that due to the chirality-flipping nature, at the 1-loop level TSIs typically generate much larger ($10^{7}\sim10^{10}$) neutrino magnetic moments ($\nu$MMs) than the vector case. For some cases, the large $\nu$MMs generated by TSIs may reach or exceed the known bounds, which implies potentially important interplay between probing TSIs and searching for $\nu$MMs in current and future neutrino experiments.Comment: Comments on effective magnetic moment add; matches the journal versio

Tree-level vacuum stability of two-Higgs-doublet models and new constraints on the scalar potential

The scalar potential of the two-Higgs-doublet model (2HDM) may have more than one local minimum and the usually considered vacuum could be located at one of them that could decay to another. This paper studies the condition that the usually considered vacuum is the global minimum which, combined with the bounded-from-below condition, will stabilize the vacuum at tree-level. We further apply these conditions to a specific 2HDM and obtain new constraints which could be important in phenomenological studies.Comment: 12 pages, references adde