Meson-exchange currents and superscaling analysis with relativistic effective mass of quasielastic electron scattering from C12

Abstract

We reanalyze the scaling properties of inclusive quasielastic electron scattering from 12 C by subtracting from the data the effects of two-particle emission. A model of relativistic meson-exchange currents (MEC) is employed within the mean field theory of nuclear matter, with scalar and vector potentials that induce an effective mass and a vector energy to the nucleons. A new phenomenological quasielastic scaling function is extracted from a selection of the data after the subtraction of the 2p-2h contribution. The resulting superscaling approach with relativistic effective mass (SuSAM*) can be used to compute the genuine quasielastic cross section without contamination of the 2p-2h channel that can then be added separately to obtain the total quasielastic plus two-nucleon emission response.

Semiempirical formula for electroweak response functions in the two-nucleon emission channel in neutrino-nucleus scattering

“…As seen in Ref. [53], the effect of the imaginary part of the propagator is to increase the contribution of the ΔF diagram and the position of the maximum. The effect of the effective mass and vector energy is to reduce the height of the peak, which partially compensates for the difference of the MEC with respect to the calculation of Refs.…”

“…[51] and for electron scattering in Refs. [50,52,53]. Here, we extend these works to deepen the study of the interaction of neutrinos with nuclei at intermediate energies and the role of the 2p2h electroweak response functions, as described in the next subsection.…”

“…In this work, we use values of k F , M Ã and E v that are obtained phenomenologically from the data of (e; e 0 ) [53].…”

“…Thus, the pion-pole diagrams (d and e) are not contributing. The isospin operators are modified to the z component instead of the AE component [53]. Only the L and T responses are present in ðe; e 0 Þ The exact calculation of the response functions R K ðq; ωÞ with this model of currents is carried out by numerical integration in seven dimensions of Eq.…”

“…[50,52]. Recently, the superscaling function has been refitted by subtraction of the MEC 2p2h cross section before performing the scaling analysis, in order to avoid double-counting when adding the MEC responses [53].…”