Nuclear response functions for the N– transition

Abstract

Parity-conserving and -violating response functions are computed for the inclusive electroexcitation of the N * (1440) (Roper) resonance in nuclear matter modeled as a relativistic Fermi gas. Using various empirical parameterizations and theoretical models of the N − N * (1440) transition form factors, the sensitivity of the response functions to details of the structure of the Roper resonance is investigated. The possibility of disentangling this resonance from the contribution of ∆ electroproduction in nuclei is addressed. Finally, the contributions of the Roper resonance to the longitudinal scaling function and to the Coulomb sum rule are also explored.

Relativistic descriptions of inclusive quasielastic electron scattering: Application to scaling and superscaling ideas

“…[41]). Whereas L data are compatible with superscaling behavior, permitting the extraction of the phenomenological function f exp L (ψ ), scaling is known to be violated in the T channel at energies above the QE peak by effects beyond the impulse approximation [20][21][22][23][24]84]. It is important to point out that, although many models based on the impulse approximation exhibit superscaling, even perfectly as the RFG, only a few of them are capable to accurately reproduce the asymmetric shape of f exp L with a significant tail extended to high transferred energies (large positive values of the scaling variable ψ ).…”

Electron- and neutrino-nucleus scattering from the quasielastic to the resonance region

“…However, the present experimental status does not allow any conclusions on the strange transition form factors, thus, we neglect them in this work and set F s i and F s A to zero. Several studies have addressed the properties of the P 11 (1440) as well as its electromagnetic and weak production [40,41,42,43,44,45,46,47]. In the works of Refs.…”

Meson-exchange currents and final-state interactions in quasielastic electron scattering at high momentum transfers

“…An exhaustive analysis of (e, e ) world data demonstrated the scaling at energy transfers ω below the quasielastic (QE) peak [1,2], namely the independence of the reduced cross sections on the momentum transfer (first-kind scaling) and on the nuclear target (second-kind scaling) when plotted versus the appropriate scaling variable. It is well known that at energies above the QE peak scaling is violated in the transverse (T ) channel by effects beyond the impulse approximation: inelastic scattering [3,4], correlations, and meson-exchange currents (MEC) in both the one-particle one-hole (1p-1h) and two-particle two-hole (2p-2h) sectors [5][6][7][8].In contrast, the available data for the longitudinal (L) response are compatible with scaling throughout the QE region and permitted [9] the extraction of a phenomenological scaling function f L . In recent work [10][11][12] it was shown that only a few models [the relativistic mean field (RMF), the semirelativistic (SR) approach with Dirac-equation-based (DEB) and a "BCS-like" model] are capable of reproducing the detailed shape of f L , while other models fail to reproduce the long tail appearing at high ω. Theses models effectively account for the major ingredients needed to describe the (e, e ) responses for intermediate-to-high momentum transfers, namely relativistic effects and an appropriate description of the effective final-state interactions (FSI).…”

“…An exhaustive analysis of (e, e ) world data demonstrated the scaling at energy transfers ω below the quasielastic (QE) peak [1,2], namely the independence of the reduced cross sections on the momentum transfer (first-kind scaling) and on the nuclear target (second-kind scaling) when plotted versus the appropriate scaling variable. It is well known that at energies above the QE peak scaling is violated in the transverse (T ) channel by effects beyond the impulse approximation: inelastic scattering [3,4], correlations, and meson-exchange currents (MEC) in both the one-particle one-hole (1p-1h) and two-particle two-hole (2p-2h) sectors [5][6][7][8].…”