Speaker
Description
A method that enables the consistent inclusion of meson-exchange currents (MEC) within
the framework of the superscaling analisys with relativistic effective mass will be presented. We
use a novel definition of the single nucleon tensor, defined as the mean value of the single-nucleon
responses by averaging with an energy distribution n(?) [1]. This single nucleon prefactor is
obtained from the 1p-1h matrix element of the OB current combined with the two body current.
The averaging definition is extended beyond the scaling region of the ψ variable characteristic
of the Fermi gas modifying the momentum distribution through a smeared Fermi distribution
[2].
In the generalized scaling analysis, the selected QE data generate a band with scatter of
20% at the maximum (highlighting the extent of scaling violation) that will be parametrized
using a simple function f (ψ ∗ ) ∗ .
Through the inclusion of MEC, we conducted a comparative analisys of the 1p-1h response
functions within the context of the RFG, RMF and SuSAM ∗ models. These responses can be
expressed in a factorized way as the product of the averaged single nucleon multiplied by the
scaling function. A reduction in the transverse response is observed, which is in accordance
with previous calculations [3][4].
In this manner, the 1p-1h cross section including MEC is calculated and compared with
the calculation without MEC and the experimental data [5][6]. Our examination shows that
in the low momentum limit, the predictions of the relativistic model align with those of the
non-relativistic model in Fermi gas. The formalism can be extended to calculate the 1p-1h
neutrino nuclear responses by including the meson exchange currents using the models already
proposed in electron scattering.
[1] P. R. Casale, J. E. Amaro, V. L. Martinez-Consentino and I. Ruiz Simo, Universe 9, no.4, 158
(2023) [arXiv:2303.03890 [nucl-th]].
[2] P. R. Casale, J. E. Amaro and M. B. Barbaro, Symmetry 15 (2023) no.9, 1709 [arXiv:2307.15783
[nucl-th]].
[3] J. E. Amaro, M. B. Barbaro, J. A. Caballero, T. W. Donnelly, C. Maieron and J. M. Udias, Phys.
Rev. C 81 (2010), [arXiv:0906.5598 [nucl-th]].
[4] J. E. Amaro, A. M. Lallena and G. Co, Nucl. Phys. A 578 (1994), 365-396 doi:10.1016/0375-
9474(94)90752-8
[5]Benhar,O.;Day,D.;Sick,I. An archive for quasi-elastic electron-nucleus scattering data [arXiv:nucl-
ex/0603032]
[6] Benhar,O.;Day,D.;Sick,I. Available online: https://www.faculty.virginia.edu/qes-archive/ C83 (2011)
045501.