5,655 research outputs found
Extraction of the atmospheric neutrino fluxes from experimental event rate data
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient
in the interpretation of the results from any atmospheric neutrino experiment.
In the standard atmospheric neutrino data analysis, these fluxes are
theoretical inputs obtained from sophisticated numerical calculations. In this
contribution we present an alternative approach to the determination of the
atmospheric neutrino fluxes based on the direct extraction from the
experimental data on neutrino event rates. The extraction is achieved by means
of a combination of artificial neural networks as interpolants and Monte Carlo
methods.Comment: 6 pages, 2 figs, to appear in the proceedings of the 2nd
International Conference on Quantum Theories and Renormalization Group in
Gravity and Cosmology, Barcelona, July 200
Heavy meson semileptonic differential decay rate in two dimensions in the large Nc
We study QCD in 1+1 dimensions in the large limit using light-front
Hamiltonian perturbation theory in the expansion. We use this formalism
to exactly compute hadronic transition matrix elements for arbitrary currents
at leading order in . We compute the semileptonic differential decay
rate of a heavy meson, , and its moments, , using the hadronic
matrix elements obtained previously. We put some emphasis in trying to
understand parity invariance. We also study with special care the kinematic
region where the operator product expansion () or
non-local effective field theories () can
be applied. We then compare with the results obtained using an effective field
theory approach based on perturbative factorization, with the focus to better
understand quark-hadron duality. At the end of the day, using effective field
theories, we have been able to obtain expressions for the moments with relative
accuracy of in the kinematic region where the
operator product expansion can be applied, and with relative accuracy of
in the kinematic region where non-local effective field
theories can be applied. These expressions agree, within this precision, with
those obtained from the hadronic result using the layer-function approximation
plus Euler-McLaurin expansion. Very good numerical agreement for the moments is
obtained between the exact result and the result using effective field
theories.Comment: 52 pages, 30 figures, references added, small modifications, some
discussion of the four dimensional case changed, journal versio
Thermal and mechanical properties of a DNA model with solvation barrier
We study the thermal and mechanical behavior of DNA denaturation in the frame
of the mesoscopic Peyrard- Bishop-Dauxois model with the inclusion of solvent
interaction. By analyzing the melting transition of a homogeneous A-T sequence,
we are able to set suitable values of the parameters of the model and study the
formation and stability of bubbles in the system. Then, we focus on the case of
the P5 promoter sequence and use the Principal Component Analysis of the
trajectories to extract the main information on the dynamical behavior of the
system. We find that this analysis method gives an excellent agreement with
previous biological results.Comment: Physical Review E (in press
Symmetry breaking and clustering in a vibrated granular gas with several macroscopically connected compartments
The spontaneous symmetry breaking in a vibro-fluidized low-density granular
gas in three connected compartments is investigated. When the total number of
particles in the system becomes large enough, particles distribute themselves
unequally among the three compartments. Particles tend to concentrate in one of
the compartments, the other two having the (relatively small) same average
number of particles. A hydrodynamical model that accurately predicts the
bifurcation diagram of the system is presented. The theory can be easily
extended to the case of an arbitrary number of connected compartments
Microscopic origin of granular ratcheting
Numerical simulations of assemblies of grains under cyclic loading exhibit
``granular ratcheting'': a small net deformation occurs with each cycle,
leading to a linear accumulation of deformation with cycle number. We show that
this is due to a curious property of the most frequently used models of the
particle-particle interaction: namely, that the potential energy stored in
contacts is path-dependent. There exist closed paths that change the stored
energy, even if the particles remain in contact and do not slide. An
alternative method for calculating the tangential force removes granular
ratcheting.Comment: 13 pages, 18 figure
Constraints on hidden gravitons from fifth-force experiments and stellar energy loss
We study different phenomenological signatures associated with new spin-2
particles. These new degrees of freedom, that we call hidden gravitons, arise
in different high-energy theories such as extra-dimensional models or
extensions of General Relativity. At low energies, hidden gravitons can be
generally described by the Fierz-Pauli Lagrangian. Their phenomenology is
parameterized by two dimensionful constants: their mass and their coupling
strength. In this work, we analyze two different sets of constraints. On the
one hand, we study potential deviations from the inverse-square law on
solar-system and laboratory scales. To extend the constraints to scales where
the laboratory probes are not competitive, we also study consequences on
astrophysical objects. We analyze in detail the processes that may take place
in stellar interiors and lead to emission of hidden gravitons, acting like an
additional source of energy loss.Comment: 15 pages, 7 figure
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