808 research outputs found
Leptogenesis with SU(5)-inspired mass matrices
In the baryogenesis via leptogenesis framework the baryonic asymmetry depends
on lepton mass matrices. In a previous paper we used SO(10)-inspired mass
matrices and we found few possibilities to obtain a sufficient level of
asymmetry. In the present paper we use SU(5)-inspired mass matrices, which also
allow to check the dependence of the baryonic asymmetry on Dirac neutrino
masses. In particular, we find that the large mixing matter solution to the
solar neutrino problem, which within SO(10) gives too small asymmetry, can now
be favoured.Comment: RevTex, 14 pages with 4 figure
Leptogenesis and Low-energy Observables
We relate leptogenesis in a class of theories to low-energy experimental
observables: quark and lepton masses and mixings. With reasonable assumptions
motivated by grand unification, one can show that the CP-asymmetry parameter
takes a universal form. Furthermore the dilution mass is related to the light
neutrino masses. Overall, these models offer a natural explanation for a lepton
asymmetry in the early universe.Comment: 10 pages, revised discussion on light neutrino masse
Fermion masses and mixings in gauge theories
The recent evidence for neutrino oscillations stimulate us to discuss again
the problem of fermion masses and mixings in gauge theories. In the standard
model, several forms for quark mass matrices are equivalent. They become
ansatze within most extensions of the standard model, where also relations
between quark and lepton sectors may hold. In a seesaw framework, these
relations can constrain the scale of heavy neutrino mass, which is often
related to the scale of intermediate or unification gauge symmetry. As a
consequence, two main scenarios arise. Hierarchies of masses and mixings may be
explained by broken horizontal symmetries.Comment: 25 pages, RevTex, no figures. Few misprints corrected and two
references adde
Multigene Editing Via CRISPR/Cas9 Guided By a Single-sgRNA Seed in Arabidopsis
We report that a single-sgRNA seed is capable of guiding CRISPR/Cas9 to simultaneously edit multiple genes AtRPL10A, AtRPL10B and AtRPL10C in Arabidopsis. Our results also demonstrate that it is possible to use CRISPR/Cas9 technology to create AtRPL10 triple mutants which otherwise cannot be generated by conventional genetic crossing. Compared to other conventional multiplex CRISPR/Cas systems, a single sgRNA seed has the advantage of reducing off-target gene-editing. Such a single sgRNA seed-induced gene editing system might be also applicable to modify other homologous genes or even less-homologous sequences for multiple gene-editing in plants and other organisms. [Abstract copyright: This article is protected by copyright. All rights reserved.
Testing quark mass matrices with right-handed mixings
In the standard model, several forms of quark mass matrices which correspond
to the choice of weak bases lead to the same left-handed mixings ,
while the right-handed mixings are not observable quantities. Instead, in
a left-right extension of the standard model, such forms are ansatze and give
different right-handed mixings which are now observable quantities. We
partially select the reliable forms of quark mass matrices by means of
constraints on right-handed mixings in some left-right models, in particular on
. Hermitian matrices are easily excluded.Comment: 12 pages RevTex, no figures. Minor corrections. Comment on SO(10)
changed and one reference adde
Seesaw mechanism, baryon asymmetry and neutrinoless double beta decay
A simplified but very instructive analysis of the seesaw mechanism is here
performed. Assuming a nearly diagonal Dirac neutrino mass matrix, we study the
forms of the Majorana mass matrix of right-handed neutrinos, which reproduce
the effective mass matrix of left-handed neutrinos. As a further step, the
important effect of a non diagonal Dirac neutrino mass matrix is explored. The
corresponding implications for the baryogenesis via leptogenesis and for the
neutrinoless double beta decay are reviewed. We propose two distinct models
where the baryon asymmetry is enhanced.Comment: 21 pages, RevTex. Revise
Connecting Leptogenesis to CP Violation in Neutrino Mixings in a Tri-bimaximal Mixing model
We show that in a recently proposed model for tri-bimaximal mixing
pattern for neutrinos, CP violating phases in neutrino mixings are directly
responsible for lepton asymmetry . In the exact tri-bimaximal
limit, is proportional to one of the Majorana phases whereas in
the presence of small deviations from tri-bimaximal pattern, there are two
contributions, one being proportional to the Dirac phase and the other to one
of the two Majorana phases. In the second case, is nonzero and
correlated with the deviation from maximal atmospheric mixing.Comment: 14 pages; no figures; references update
Consequences of Triplet Seesaw for Leptogenesis
We present the various leptogenesis scenarios which may occur if, in addition
to the ordinary heavy right-handed neutrinos, there exists a heavy scalar
SU(2)_L triplet coupled to leptons. We show that the contributions of the
right-handed neutrinos and the triplet to the lepton asymmetry are proportional
to their respective contributions to the neutrino mass matrix. A consequence of
the triplet contribution to the lepton asymmetry is that there is no more upper
bound on the neutrino masses from leptogenesis due to the fact that the
neutrino mass constraints do not necessarily induce asymmetry washout effects.
We also show how such a triplet leptogenesis mechanism may emerge naturally in
the framework of the left-right symmetric theories, such as Pati-Salam or
SO(10).Comment: 13 pages; references added, 2 footnotes modifie
Leptogenesis and neutrino parameters
We calculate the baryonic asymmetry of the universe in the
baryogenesis-via-leptogenesis framework, assuming first a quark-lepton symmetry
and then a charged-neutral lepton symmetry. We match the results with the
experimentally favoured range. In the first case all the oscillation solutions
to the solar neutrino problem, except the large mixing matter solution, can
lead to the allowed range, but with fine tuning of the parameters. In the
second case the general result is quite similar. Some related theoretical hints
are discussed.Comment: RevTex, 21 pages with 8 figure
S_3 Flavor Symmetry and Leptogenesis
We consider leptogenesis in a minimal
S_3 extension of the standard model with an additional Z_2 symmetry in the
leptonic sector. It is found that the CP phase appearing in the neutrino mixing
is the same as that for the CP asymmetries responsible for leptogenesis.
Because of the discrete S_3 x Z_2 flavor symmetries, the CP asymmetries are
strongly suppressed. We therefore assume that the resonant enhancement of the
CP asymmetries takes place to obtain a realistic size of baryon number
asymmetry in theuniverse. Three degenerate right-handed neutrino masses of
O(10) TeV are theoretically expected in this model.Comment: 25 pages, 3 figure
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