31,460 research outputs found
Two Particle-Hole Excitations in Charged Current Quasielastic Antineutrino--Nucleus Scattering
We evaluate the quasielastic and multinucleon contributions to the
antineutrino nucleus scattering cross section and compare our results with the
recent MiniBooNE data. We use a local Fermi gas model that includes RPA
correlations and gets the multinucleon part from a systematic many body
expansion of the boson selfenergy in the nuclear medium. The same model had
been quite successful for the neutrino cross section and contains no new
parameters. We have also analysed the relevance of 2p2h events for the
antineutrino energy reconstruction.Comment: 6 pages, 4 figure
Global superscaling analysis of quasielastic electron scattering with relativistic effective mass
We present a global analysis of the inclusive quasielastic electron
scattering data with a superscaling approach with relativistic effective mass.
The SuSAM* model exploits the approximation of factorization of the scaling
function out of the cross section under quasifree conditions. Our
approach is based on the relativistic mean field theory of nuclear matter where
a relativistic effective mass for the nucleon encodes the dynamics of nucleons
moving in presence of scalar and vector potentials. Both the scaling variable
and the single nucleon cross sections include the effective mass as a
parameter to be fitted to the data alongside the Fermi momentum . Several
methods to extract the scaling function and its uncertainty from the data are
proposed and compared. The model predictions for the quasielastic cross section
and the theoretical error bands are presented and discussed for nuclei along
the periodic table from to : H, H, He, He,
C, Li, Be, Mg, Ni,
Y, Sn, Ta, W, Au, O, Al,
Ca, Ca, Fe, Pb, and U.
We find that more than 9000 of the total data fall within the
quasielastic theoretical bands. Predictions for Ti and Ar are
also provided for the kinematics of interest to neutrino experiments.Comment: 26 pages, 20 figures and 4 table
A numerical study of planar arrays of correlated spin islands
We present our analysis of a system of interacting islands of XY spins on a
triangular lattice that has been introduced a few years ago by Eley et al. to
account for the phenomenology in experiments on tunable arrays of proximity
coupled long superconductor-normal metal-superconductor junctions. The main
features of the model are the separation of a local and a global interaction
energy scale and the mesoscopic character of the spin islands. Upon lowering
the temperature the model undergoes two crossovers corresponding to an
increasing phase coherence on a single island and to the onset of global
coherence across the array; the latter is a thermodynamical phase transition in
the Ising universality class. The dependence of the second transition on the
island edge-to-edge spacing is related to the proximity-effect of the coupling
constant.Comment: 6 pages, 5 figures, accepted for publication in EPJ
Study of the derivative expansions for the nuclear structure functions
We study the convergence of the series expansions sometimes used in the
analysis of the nuclear effects in Deep Inelastic Scattering (DIS) proccesses
induced by leptons. The recent advances in statistics and quality of the data,
in particular for neutrinos calls for a good control of the theoretical
uncertainties of the models used in the analysis. Using realistic nuclear
spectral functions which include nucleon correlations, we find that the
convergence of the derivative expansions to the full results is poor except at
very low values of
Neutrino Energy Reconstruction and the Shape of the CCQE-like Total Cross Section
We show that because of the multinucleon mechanism effects, the algorithm
used to reconstruct the neutrino energy is not adequate when dealing with
quasielastic-like events, and a distortion of the total flux unfolded cross
section shape is produced. This amounts to a redistribution of strength from
high to low energies, which gives rise to a sizable excess (deficit) of low
(high) energy neutrinos. This distortion of the shape leads to a good
description of the MiniBooNE unfolded CCQE-like cross sections published in
Phys.Rev. D81 (2010) 092005. However, these changes in the shape are artifacts
of the unfolding process that ignores multinucleon mechanisms.Comment: 11 pages, 6 figures. Some references and comments adde
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