28,376 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
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
FRW in cosmological self-creation theory: Hamiltonian approach
We use the Brans-Dicke theory from the framework of General Relativity
(Einstein frame), but now the total energy momentum tensor fulfills the
following condition . We take as a first model the flat FRW metric in the
Hamilton-Jacobi scheme and we present the Lagrange-Charpit approach in order to
find classical solutions. In the quantum scheme, once we determine the
characteristic surfaces, the quantum solution is obtained. These two classes of
solutions are found for all values of the barotropic parameter .Comment: 9 pages, latex2e. arXiv admin note: substantial text overlap with
arXiv:1206.541
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