1,220 research outputs found

### $\sin{\theta}_{13}$ and neutrino mass matrix with an approximate flavor symmetry

For a neutrino mass matrix whose texture has an approximate flavor symmetry
and where one has near degenerate neutrino mass, it is shown that the
tribimaximal values for atmospheric angle $\sin^{2}{\theta_{23}}=1/2$ and solar
angle $\sin^{2}{\theta_{12}}=1/3$ can be maintained even when the reactor angle
$\theta_{13}\neq0$. The non zero $\sin\theta_{13}$ implies approximate
$\nu_{\mu}\rightarrow-\nu_{\tau}$ symmetry instead of
$\nu_{\mu}\rightarrow\nu_{\tau}$ symmetry.Comment: 13 pages,2 figures, Published in JHE

### On the branching ratio of the "second class" tau --> eta' pi nu_tau decay

We present an assessment of the standard model expectations for the branching
ratio of the isotopic spin and G-parity violating decay tau --> eta' pi nu_tau.
The estimate is based on a vector and scalar meson dominance parametrization of
the relevant form factors, that explicitly accounts for pi^0-eta-eta' mixing.
The numerical results obtained in this framework indicate a branching ratio one
order of magnitude (or more) below the current experimental limit, and suggest
the possibility of evidencing some novel interaction in high statistics studies
of this decay.Comment: 8 page

### Dirac equation for quasi-particles in graphene and quantum field theory of their Coulomb interaction

There is evidence for existence of massless Dirac quasi-particles in
graphene, which satisfy Dirac equation in (1+2) dimensions near the so called
Dirac points which lie at the corners at the graphene's brilluoin zone. We
revisit the derivation of Dirac equation in (1+2) dimensions obeyed by
quasiparticles in graphene near the Dirac points. It is shown that parity
operator in (1+2) dimensions play an interesting role and can be used for
defining "conserved" currents resulting from the underlying Lagrangian for
Dirac quasi-particles in graphene which is shown to have U_{A}(1)*U_{B}(1)
symmetry. Further the quantum field theory (QFT) of Coulomb interaction of 2D
graphene is developed and applied to vacuum polarization and electron self
energy and the renormalization of the effective coupling g of this interaction
and Fermi velocity $v_{f}$ which has important implications in the
renormalization group analysis of g and v_{f}.Comment: 10 pages, some typos have been corrected, some references have been
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