35 research outputs found
Semi-leptonic (1968) decays as a scalar meson probe
The unusual multiplet structures associated with the light spin zero mesons
have recently attracted a good deal of theoretical attention. Here we discuss
some aspects associated with the possibility of getting new experimental
information on this topic from semi-leptonic decays of heavy charged mesons
into an isosinglet scalar or pseudoscalar plus leptons.Comment: 11 pages, 4 figure
An approach to permutation symmetry for the electroweak theory
The form of the leptonic mixing matrix emerging from experiment has, in the
last few years, generated a lot of interest in the so-called tribimaximal type.
This form may be naturally associated with the possibility of a discrete
permutation symmetry () among the three generations. However, trying to
implement this attractive symmetry has resulted in some problems and it seems
to have fallen out of favor. We suggest an approach in which the holds to
first approximation, somewhat in the manner of the old SU(3) flavor symmetry of
the three flavor quark model. It is shown that in the case of the neutrino
sector, a presently large experimentally allowed region can be fairly well
described in this first approximation.
We briefly discuss the nature of the perturbations which are the analogs of
the Gell-Mann Okubo perturbations but confine our attention for the most part
to the invariant model. We postulate that the invariant mass
spectrum consists of non zero masses for the and zero masses for
the other charged fermions but approximately degenerate masses for the three
neutrinos. The mixing matrices are assumed to be trivial for the charged
fermions but of tribimaximal type for the neutrinos in the first approximation.
It is shown that this can be implemented by allowing complex entries for the
mass matrix and spontaneous breakdown of the invariance of the
Lagrangian.Comment: 24 pages, 1 figure, minor corrections and acknowledgment added. To
appear in IJM
Toy model for two chiral nonets
Motivated by the possibility that nonets of scalar mesons might be described
as mixtures of "two quark" and "four quark" components, we further study a toy
model in which corresponding chiral nonets (containing also the pseudoscalar
partners) interact with each other. Although the "two quark" and "four quark"
chiral fields transform identically under SU(3) SU(3)
transformations they transform differently under the U(1) transformation
which essentially counts total (quark + antiquark) content of the mesons. To
implement this we formulate an effective Lagrangian which mocks up the U(1)
behavior of the underlying QCD. We derive generating equations which yield Ward
identity type relations based only on the assumed symmetry structure. This is
applied to the mass spectrum of the low lying pseudoscalars and scalars. as
well as their "excitations". Assuming isotopic spin invariance, it is possible
to disentangle the amount of"two quark" vs."four quark" content in the
pseudoscalar type states and in the scalar type states.
It is found that a small "four quark" content in the lightest pseudoscalars is
consistent with a large "four quark" content in the lightest of the scalar
mesons. The present toy model also allows one to easily estimate the
strength of a "four quark" vacuum condensate. There seems to be a rich and
interesting structure.Comment: Numerical results updated, typos corrected, references update
Broken S3 Symmetry in the Neutrino Mass Matrix and Non-Zero theta_{13}
We study the effects of breaking S3 symmetry in the neutrino mass matrix for
the masses and mixing matrix of neutrinos. At zeroth order the model gives
degenerate neutrino masses and accommodates tribimaximal mixing. We introduce
perturbations in terms of a small and complex parameter. The perturbations are
introduced in a manner such that the S3 symmetry is broken by its elements in
the same representation. Successive perturbations introduce mass splitting,
sizable non-zero reactor mixing angle and CP violation. This scheme of breaking
S3 symmetry can reproduce a relatively large reactor mixing angle as suggested
by the recent T2K results. The effective neutrino mass is predicted to be large
which is testable in the ongoing and forthcoming neutrinoless double beta decay
experiments.Comment: 14 pages, 4 figures, 1 table, references adde
Quantum gauge models without classical Higgs mechanism
We examine the status of massive gauge theories, such as those usually
obtained by spontaneous symmetry breakdown, from the viewpoint of causal
(Epstein-Glaser) renormalization. The BRS formulation of gauge invariance in
this framework, starting from canonical quantization of massive (as well as
massless) vector bosons as fundamental entities, and proceeding perturbatively,
allows one to rederive the reductive group symmetry of interactions, the need
for scalar fields in gauge theory, and the covariant derivative. Thus the
presence of higgs particles is explained without recourse to a
Higgs(-Englert-Brout-Guralnik-Hagen-Kibble) mechanism. Along the way, we dispel
doubts about the compatibility of causal gauge invariance with grand unified
theories.Comment: 20 pages in two-column EPJC format, shortened version accepted for
publication. For more details, consult version
Production of selenium nanoparticles in Pseudomonas putida KT2440
Selenium (Se) is an essential element for the cell that has multiple applications in medicine and technology; microorganisms play an important role in Se transformations in the environment. Here we report the previously unidentified ability of the soil bacterium Pseudomonas putida KT2440 to synthesize nanoparticles of elemental selenium (nano-Se) from selenite. Our results show that P. putida is able to reduce selenite aerobically, but not selenate, to nano-Se. Kinetic analysis indicates that, in LB medium supplemented with selenite (1 mM), reduction to nano-Se occurs at a rate of 0.444 mmol L−1 h−1 beginning in the middle-exponential phase and with a final conversion yield of 89%. Measurements with a transmission electron microscope (TEM) show that nano-Se particles synthesized by P. putida have a size range of 100 to 500 nm and that they are located in the surrounding medium or bound to the cell membrane. Experiments involving dynamic light scattering (DLS) show that, in aqueous solution, recovered nano-Se particles have a size range of 70 to 360 nm. The rapid kinetics of conversion, easy retrieval of nano-Se and the metabolic versatility of P. putida offer the opportunity to use this model organism as a microbial factory for production of selenium nanoparticles.Universidad de Costa Rica/[809-B5-A68]/UCR/Costa RicaCentro Nacional de Innovaciones Biotecnológicas/[]/CENIBiot/Costa RicaBio-SEA/[]//FranciaUCR::VicerrectorÃa de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Estructuras Microscópicas (CIEMIC)UCR::VicerrectorÃa de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de QuÃmicaUCR::VicerrectorÃa de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en ElectroquÃmica y EnergÃa QuÃmica (CELEQ)UCR::VicerrectorÃa de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones en Productos Naturales (CIPRONA
Solation of Citric Acid From Microorganisms
Citric acid is widely used in medicine, food, chemical and light industries. According to the data, the world production of citric acid is 400 thousand tons per year. This article describes the fermentation steps in citric acid production, industrial synthesis, shallow culture, and liquid culture