37,878 research outputs found
Constraining New Physics with D meson decays
Latest Lattice results on form factors evaluation from first principles
show that the standard model (SM) branching ratios prediction for the leptonic
decays and the semileptonic SM branching ratios of the
and meson decays are in good agreement with the world average
experimental measurements. It is possible to disprove New Physics hypothesis or
find bounds over several models beyond the SM. Using the observed leptonic and
semileptonic branching ratios for the D meson decays, we performed a combined
analysis to constrain non standard interactions which mediate the transition. This is done either by a model independent way through
the corresponding Wilson coefficients or in a model dependent way by finding
the respective bounds over the relevant parameters for some models beyond the
standard model. In particular, we obtain bounds for the Two Higgs Doublet Model
Type-II and Type III, the Left-Right model, the Minimal Supersymmetric Standard
Model with explicit R-Parity violation and Leptoquarks. Finally, we estimate
the transverse polarization of the lepton in the decay and we found it
can be as high as .Comment: 28 pages, 8 figures, 3 tables. Improved and extended analysis with
updated form factors from Lattice QC
Scattering processes could distinguish Majorana from Dirac neutrinos
It is well known that Majorana neutrinos have a pure axial neutral current
interaction while Dirac neutrinos have the standard vector-axial interaction.
In spite of this crucial difference, usually Dirac neutrino processes differ
from Majorana processes by a term proportional to the neutrino mass, resulting
in almost unmeasurable observations of this difference. In the present work we
show that once the neutrino polarization evolution is considered, there are
clear differences between Dirac and Majorana scattering on electrons. The
change of polarization can be achieved in astrophysical environments with
strong magnetic fields. Furthermore, we show that in the case of unpolarized
neutrino scattering onto polarized electrons, this difference can be relevant
even for large values of the neutrino energy.Comment: 12 pages, 5 figure
Magnetic field-induced insulating behavior in highly oriented pyrolitic graphite
We propose an explanation for the apparent semimetal-insulator transition
observed in highly oriented pyrolitic graphite in the presence of magnetic
field perpendicular to the layers. We show that the magnetic field opens an
excitonic gap in the linear spectrum of the Coulomb interacting quasiparticles,
in a close analogy with the phenomenon of dynamical chiral symmetry breaking in
the relativistic theories of the 2+1-dimensional Dirac fermions. Our
strong-coupling appoach allows for a non-perturbative description of the
corresponding critical behavior
Constructing networks of defects with scalar fields
We propose a new way to build networks of defects. The idea takes advantage
of the deformation procedure recently employed to describe defect structures,
which we use to construct networks, spread from small rudimentary networks that
appear in simple models of scalar fields.Comment: 5 pages, 4 figures, version with new title, motivations and
references, to appear in PL
Exploring Rigidly Rotating Vortex Configurations and their Bifurcations in Atomic Bose-Einstein Condensates
In the present work, we consider the problem of a system of few vortices as it emerges from its experimental realization in the field of atomic
Bose-Einstein condensates. Starting from the corresponding equations of motion,
we use a two-pronged approach in order to reveal the configuration space of the
system's preferred dynamical states. On the one hand, we use a Monte-Carlo
method parametrizing the vortex "particles" by means of hyperspherical
coordinates and identifying the minimal energy ground states thereof for and different vortex particle angular momenta. We then complement this
picture with a dynamical systems analysis of the possible rigidly rotating
states. The latter reveals all the supercritical and subcritical pitchfork, as
well as saddle-center bifurcations that arise exposing the full wealth of the
problem even at such low dimensional cases. By corroborating the results of the
two methods, it becomes fairly transparent which branch the Monte-Carlo
approach selects for different values of the angular momentum which is used as
a bifurcation parameter.Comment: 12 pages, 7 figures. New improved result
Solar System experiments do not yet veto modified gravity models
The dynamical equivalence between modified and scalar-tensor gravity theories
is revisited and it is concluded that it breaks down in the limit to general
relativity. A gauge-independent analysis of cosmological perturbations in both
classes of theories lends independent support to this conclusion. As a
consequence, the PPN formalism of scalar-tensor gravity and Solar System
experiments do not veto modified gravity, as previously thought.Comment: 7 pages, latex, submitted to Phys. Rev.
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