4,553 research outputs found
Coherent pion production off nuclei at T2K and MiniBooNE energies revisited
As a result of a new improved fit to old bubble chamber data of the dominant
axial C_5^A nucleon-to-Delta form factor, and due to the relevance of this form
factor for neutrino induced coherent pion production, we re-evaluate our model
predictions in Phys. Rev. D79, 013002 (2009) for different observables of the
latter reaction. Central values for the total cross sections increase by 20% to
30%, while differential cross sections do not change their shape appreciably.
Furthermore, we also compute the uncertainties on total, differential and flux
averaged cross sections induced by the errors in the determination of C_5^A.
Our new results turn out to be compatible within about 1 sigma with the former
ones. Finally, we stress the existing tension between the recent experimental
determination of the sigma(CC coh \pi^+)/sigma(NC coh \pi^0) ratio by the
SciBooNE Collaboration and the theoretical predictions.Comment: 6 latex pages, 1 table, 2 figures. Shortened versio
Nucleon Emision Off Nuclei Induced By Neutrino Interactions
We make a review of the main nuclear effects that affect neutrino-nucleus
cross sections. We discuss how the different models in the literature try to
describe these different effects, and thus try to compare between them. We
focus on the quasi-elastic reaction in the neutrino energy region of around 1
GeV, where recent data from MiniBoone are available. Among the issues discussed
are the different treatment of medium corrections to initial and nal state
nucleon wave functions and the problem of the rescattering of ejected nucleons.Comment: 5 pages, 5 figures. To appear in the proceedings for NuFact09; July
20-25, (2009) Illinois Institute of Technolog
New determination of the - axial form factors from weak pion production and coherent pion production off nuclei at T2K and MiniBooNE energies revisited
We re-evaluate our model predictions in Phys. Rev. D 79, 013002 (2009) for
different observables in neutrino induced coherent pion production. This comes
as a result of the new improved fit to old bubble chamber data of the dominant
axial C_5^A nucleon-to-Delta form factor. We find an increase of 20%-30% in the
values for the total cross sections. Uncertainties induced by the errors in the
determination of C_5^A are computed. Our new results turn out to be compatible
within about with the former ones. We also stress the existing
tension between the recent experimental determination of the \sigma(CC coh
\pi^+)}/\sigma(NC coh \pi^0)} $ ratio by the SciBooNE Collaboration and the
theoretical predictions.Comment: 3 latex pages, 1 figure. Talk given at the NuFact10 Conferenc
Neutrino induced coherent pion production
We discuss different parameterizations of the axial
form factor, fitted to the old Argonne bubble chamber data for pion production
by neutrinos, and we use coherent pion production to test their low
behavior. We find moderate effects that will be difficult to observe with the
accuracy of present experiments. We also discuss the use of the Rein-Sehgal
model for low energy coherent pion production. By comparison to a microscopic
calculation, we show the weaknesses of some of the approximations in that model
that lead to very large cross sections as well as to the wrong shapes for
differential ones. Finally we show that models based on the partial
conservation of the axial current hypothesis are not fully reliable for
differential cross sections that depend on the angle formed by the pion and the
incident neutrino.Comment: Talk given at NUFACT09. 6 latex pages, 7 figures, 1 tabl
Local Fermi gas in inclusive muon capture from nuclei
We compare local Fermi gas and shell model in muon capture in nuclei in order
to estimate the effect of finite nuclear size in low energy weak reactions.Comment: 6 pages, 8 figures. To be published in the Proceedings of 20th Max
Born Symposium, Wroclaw (Poland), December 7-10, 200
Logarithmic growth dynamics in software networks
In a recent paper, Krapivsky and Redner (Phys. Rev. E, 71 (2005) 036118)
proposed a new growing network model with new nodes being attached to a
randomly selected node, as well to all ancestors of the target node. The model
leads to a sparse graph with an average degree growing logarithmically with the
system size. Here we present compeling evidence for software networks being the
result of a similar class of growing dynamics. The predicted pattern of network
growth, as well as the stationary in- and out-degree distributions are
consistent with the model. Our results confirm the view of large-scale software
topology being generated through duplication-rewiring mechanisms. Implications
of these findings are outlined.Comment: 7 pages, 3 figures, published in Europhysics Letters (2005
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