1,715 research outputs found
Probing neutrino magnetic moment and unparticle interactions with Borexino
We discuss the limits on the neutrino magnetic moment and hypothetical
interactions with a hidden unparticle sector, coming from the first neutrino
data release of the Borexino experiment. The observed spectrum in Borexino
depends weakly on the solar model used in the analysis, since most of the
signal comes from the mono-energetic 7Be neutrinos. This fact allows us to
calibrate the nu-e scattering cross section through the spectral shape. In this
way, we have derived a limit on the magnetic moment for the neutrinos coming
from the Sun (in which a nu_mu and nu_tau component is present): mu_nu<8.4E-11
mu_B (90%CL) which is comparable with those obtained from low energy reactor
experiments. Moreover, we improve the previous upper limit on magnetic moment
of the nu_tau by three orders of magnitude and the limit on the coupling
constant of the neutrino with a hidden unparticle sector.Comment: 16 pages, 3 figures. Some clarifications and references added.
Accepted for publication in Phys. Rev.
The flavor physics in unified gauge theory from an S_3*P discrete symmetry
We investigate the phenomenological implication of the discrete symmetry
S_3*P on flavor physics in SO(10) unified theory. We construct a minimal
renormalizable model which reproduces all the masses and mixing angle of both
quarks and leptons. As usually the SO(10) symmetry gives up to relations
between the down sector and the charged lepton masses. The underlining discrete
symmetry gives a contribution (from the charged lepton sector) to the PMNS
mixing matrix which is bimaximal. This gives a strong correlation between the
down quark and charged lepton masses, and the lepton mixing angles. We obtain
that the small entries V_{ub}, V_{cb}, V_{td}, and V_{ts} in the CKM matrix are
related to the small value of the ratio "dm^2_{sol}/dm^2_{atm}": they come from
both the S_2*P structure of our model and the small ratio of the other quark
masses with respect to m_t.Comment: 5 pages, revtex4. v2: published versio
Neutrino Mass Matrices with Vanishing Determinant and
We investigate the prospects for scenarios with vanishing determinant
neutrino mass matrices and vanishing mixing angle. Normal and
inverse mass hierarchies are considered separately. For normal hierarchy it is
found that neutrinoless double beta decay cannot be observed by any of the
present or next generation experiments. For inverse hierarchy the neutrinoless
double beta decay is, on the contrary, accessible to experiments. We also
analyse for both hierarchies the case for texture zeros and equalities between
mass matrix elements. No texture zeros are found to be possible nor any such
equalities, apart from the obvious ones.Comment: 14 pages, 1 figur
Intra-specific variability and unusual organization of the repetitive units in a satellite DNA from Rana dalmatina: molecular evidence of a new mechanism of DNA repair acting on satellite DNA.
We have characterized the S1 satellite from eight European populations of Rana dalmatina by Southern blot, cloning and a new method that determines the sequence variability of repetitive units in the genome. This report completes our previous studies on this satellite DNA family, thus providing the first characterization of the overall variability of the structure and genomic organization of a satellite DNA within a species and among related species. The S1 satellite from R. dalmatina has a pericentromeric location on ten chromosome pairs and presents two homologous repeats S1a (494 bp) and S1b (332 bp), mostly organized as composite S1a-S1b repetitive units. In other brown frog species, both repeats have different sequences and locations, and are usually organized as separate arrays, although composite S1a-S1b repeats represent a minor, widely variable component in Rana italica. The average genomic sequences indicate that the species contains an enormous number of variants of each repeat derived from a unique, species-specific common sequence. The repeat variability is restricted to specific base changes in specific sequence positions in all population samples. Our data show that the structure and evolution of S1 satellite family is not due to crossing-over and gene conversion, but to a mechanism that maintains the ability of the satellite DNA to assemble in constitutive heterochromatin by replacing altered satellite segments with new arrays generated by rolling circle amplification. The mode of action of this repair process not only directly explains the intra- and inter-specific variability of the structure and organization of the S1 satellite repeats from European brown frogs, but also accounts for all general features of satellite DNA in eukaryotes, including its discontinuous evolution. This repair mechanism can maintain the satellite structure in a species indefinitely, but also promote a rapid generation of new variants or types of satellite DNA when environmental conditions favor the formation of new species
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