3,532 research outputs found

### 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

### Why Is The Neutrino Oscillation Formula Expanded In $\Delta m_{21}^{2}/\Delta m_{31}^{2}$ 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

### 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

### Trimaximal $\mu$-$\tau$ reflection symmetry

The $\mu$-$\tau$ reflection symmetry
$(\nu_{e},\thinspace\nu_{\mu},\thinspace\nu_{\tau})\rightarrow(\overline{\nu}_{e},\thinspace\overline{\nu}_{\tau},\thinspace\overline{\nu}_{\mu})$
and the TM1 mixing (a PMNS matrix with the first column fixed to the TBM form)
are both well compatible with experiments. If both approaches are
simultaneously assumed, all lepton mixing parameters except for $\theta_{13}$
are predicted. In particular, one expects maximal CP violation
($|\delta|=90^{\circ}$), maximal atmospheric mixing ($\theta_{23}=45^{\circ}$),
a slightly less-than-TBM solar mixing angle ($\theta_{12}\approx34^{\circ}$),
as well as values of $0$ or $\pi$ for the two Majorana phases. We study the
renormalization stability of this highly predictive framework when neutrino
mass is described by an effective Weinberg operator and by the type I seesaw
mechanism, both in the Standard Model and with supersymmetry.Comment: 12 pages, comments added, version to appear in PR

### Origin of Symmetric PMNS and CKM Matrices

The PMNS and CKM matrices are phenomenologically close to symmetric, and a
symmetric form could be used as zeroth-order approximation for both matrices.
We study the possible theoretical origin of this feature in flavor symmetry
models. We identify necessary geometric properties of discrete flavor symmetry
groups that can lead to symmetric mixing matrices. Those properties are
actually very common in discrete groups such as $A_{4}$, $S_{4}$ or
$\Delta(96)$. As an application of our theorem, we generate a symmetric lepton
mixing scheme with
$\theta_{12}=\theta_{23}=36.21^{\circ};\theta_{13}=12.20^{\circ}$ and
$\delta=0$, realized with the group $\Delta(96)$.Comment: 8 pages. 4 figures. minor corrections to appear in PR

### A left-right symmetric flavor symmetry model

We discuss flavor symmetries in left-right symmetric theories. We show that
such frameworks are a different environment for flavor symmetry model building
compared to the usually considered cases. This does not only concern the need
to obey the enlarged gauge structure, but also more subtle issues with respect
to residual symmetries. Furthermore, if the discrete left-right symmetry is
charge conjugation, potential inconsistencies between the flavor and charge
conjugation symmetries should be taken care of. In our predictive model based
on $A_4$ we analyze the correlations between the smallest neutrino mass, the
atmospheric mixing angle and the Dirac CP phase, the latter prefers to lie
around maximal values. There is no lepton flavor violation from the Higgs
bi-doublet.Comment: 10 pages, 5 figure

### Robustness of Neutrino Mass Matrix Predictions

We investigate the stability of neutrino mass matrix predictions on important
and currently unknown observables. Those are the octant of $\theta_{23}$, the
sign of $\sin\delta$ and the neutrino mass ordering. Determining those unknowns
is expected to be useful in order to distinguish neutrino mass models.
Therefore it may be interesting to know how robust the predictions of a mass
matrix for the octant of $\theta_{23}$ or the neutrino mass ordering are. By
applying general multiplicative perturbations we explicitly quantify how
probable it is that a perturbed mass matrix predicts an octant of $\theta_{23}$
different from the original mass matrix, or even a neutrino mass ordering
different from the original one. Both the general case and an explicit flavor
symmetry model are studied. We give the probabilities as a function of the
smallest neutrino mass, showing that for values exceeding 0.1 eV the chance to
switch the prediction quickly approaches $50\,\%$.Comment: 8 pages,10 figures, published by NP

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