3,713 research outputs found
Seesaw mirroring between light and heavy Majorana neutrinos with the help of the reflection symmetry
In the canonical seesaw mechanism we require the relevant neutrino mass terms
to be invariant under the charge-conjugation transformations of left-
and right-handed neutrino fields. Then both the Dirac mass matrix and the right-handed neutrino mass matrix are well
constrained, so is the effective light Majorana neutrino mass matrix
via the seesaw formula. We find that these mass matrices can be classified into
22 categories, among which some textures respect the well-known -
permutation or reflection symmetry and flavor democracy. It is also found that
there exist remarkable structural equalities or similarities between
and , reflecting a seesaw mirroring relationship between light
and heavy Majorana neutrinos. We calculate the corresponding light neutrino
masses and flavor mixing parameters as well as the CP-violating asymmetries in
decays of the lightest heavy Majorana neutrino, and show that only the flavored
leptogenesis mechanism is possible to work for three categories of and in the reflection symmetry limit.Comment: 33 pages, 1 table. v2: matches the version accepted for publication
in JHE
Reconstruction of the Neutrino Mixing Matrix and Leptonic Unitarity Triangles from Long-baseline Neutrino Oscillations
We derive a new set of sum rules between the neutrino mass and mixing
parameters in vacuum and their effective counterparts in matter. The moduli of
nine genuine lepton mixing matrix elements can then be calculated in terms of
the matter-corrected ones, and the latter can directly be determined from a
variety of long-baseline neutrino oscillations. We show that it is possible to
reconstruct the leptonic unitarity triangles and CP violation in a similar
parametrization-independent way.Comment: 12 pages, 1 figur
The breaking of flavor democracy in the quark sector
The democracy of quark flavors is a well-motivated flavor symmetry, but it
must be properly broken in order to explain the observed quark mass spectrum
and flavor mixing pattern. We reconstruct the texture of flavor democracy
breaking and evaluate its strength in a novel way, by assuming a parallelism
between the Q=+2/3 and Q=-1/3 quark sectors and using a nontrivial
parametrization of the flavor mixing matrix. Some phenomenological implications
of such democratic quark mass matrices, including their variations in the
hierarchy basis and their evolution from the electroweak scale to a
superhigh-energy scale, are also discussed.Comment: 14 pages. References added. Accepted for publication in Chinese Phys.
Generalized Friedberg-Lee model for neutrino masses and leptonic CP violation from mu-tau symmetry breaking
Assuming the Majorana nature of massive neutrinos, we generalize the
Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass
matrix M_\nu. The most general case with all the free parameters of M_\nu being
complex is discussed. We show that a favorable neutrino mixing pattern (with
\theta_12 \approx 35.3^\circ, \theta_23=45^\circ, \theta_13 \neq 0^\circ and
\delta=90^\circ) can naturally be derived from M_\nu, if it has an approximate
or softly-broken \mu-\tau symmetry. We also point out a different way to obtain
the nearly tri-bimaximal neutrino mixing pattern with \delta=0^\circ and
non-vanishing Majorana phases.Comment: 4 pages. Talk given by He Zhang at the 4th International Conference
on Flavor Physics, 24-28 September 2007, Beijing (to appear in the
proceedings
On the Symmetry Foundation of Double Soft Theorems
Double-soft theorems, like its single-soft counterparts, arises from the
underlying symmetry principles that constrain the interactions of massless
particles. While single soft theorems can be derived in a non-perturbative
fashion by employing current algebras, recent attempts of extending such an
approach to known double soft theorems has been met with difficulties. In this
work, we have traced the difficulty to two inequivalent expansion schemes,
depending on whether the soft limit is taken asymmetrically or symmetrically,
which we denote as type A and B respectively. We show that soft-behaviour for
type A scheme can simply be derived from single soft theorems, and are thus
non-preturbatively protected. For type B, the information of the four-point
vertex is required to determine the corresponding soft theorems, and thus are
in general not protected. This argument can be readily extended to general
multi-soft theorems. We also ask whether unitarity can be emergent from
locality together with the two kinds of soft theorems, which has not been fully
investigated before.Comment: 45 pages, 7 figure
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