ΔElectroproduction and Inelastic Charge Scattering from Carbon and Iron

Abstract

Electroproduction of the A isobar in C and Fe has been studied for incident electrons with energies between 0.6 and 1.6 GeV. A longitudinal-transverse decomposition of the inclusive cross section has been made for qj =0.1 (GeV/c) 2 . The residual longitudinal cross sections measured do not provide the additional strength needed above the quasifree region to satisfy the Coulomb sum rule. The transverse cross sections are in good agreement with data from photoabsorption.PACS numbers: 25.30.Fj Excitation of the A(3,3) resonance is the dominant feature of electromagnetic and hadronic interactions with nuclei in the region of energy transfer between pion threshold and 500 MeV. Because of strong interactions with other nucleons in the nuclear interior, one expects the A to be broadened and possibly shifted in energy when excited as a constituent nucleon in nuclear matter. The nuclear response in inelastic electron scattering has been studied 1 " 3 in the A region for energy transfers to the nucleus up to 550 MeV. To date, theoretical models for electron scattering have not given a satisfactory description of the data. 4 Although calculations which include nuclear-medium effects do predict a reduction of the peak cross section and a spreading of the A width, they do not account for the -34% enhancement in the integrated strength which O'Connell et al. 4 observe in the A region. It has been speculated that the origin of this enhancement may be a "quasideuteron electrodisintegration" mode of excitation 5,6 which is strongest in the region between the quasifree peak and the A peak in the nuclear response function.The experiment reported here extends high-energy (> 1.5 GeV) measurements to the medium-heavy nucleus, Fe, and includes for the first time a longitudinaltransverse decomposition of the inclusive cross section from pion threshold through the A region. Such a decomposition is vital to understanding the nuclear response to relatively large transfers of energy and momentum. The new data provide limits on the contributions of charge-dependent processes including the lond\ dndco ^M 1 9/f R L (q,(a) + qi + tan 2 -gitudinal tail of quasifree scattering into the A region. Because A excitation on the free nucleon results from a transverse yNA coupling, experimental sensitivity to A processes is increased in the transverse component of the inclusive cross section.The experiment was performed at the Stanford Linear Accelerator Laboratory with the NPAS (Nuclear Physics at SLAC) facility. Electron beams with energies of 653, 1300, 1500, and 1650 MeV were scattered from natural targets of C and Fe. Scattered electrons were observed in the 8-GeV/c spectrometer whose detector system includes a gas Cherenkov counter, ten planes of wire chambers, and a total-absorbing segmented leadglass shower detector array. The thicknesses of the carbon and iron targets were 324 and 122 mg/cm 2 , respectively. Observation of elastic scattering from a hydrogen target provided the absolute calibration of the spectrometer. Cross sections for the C ...

Test of Fermi gas model and plane-wave impulse approximation against electron-nucleus scattering data

“…[10] (filled circles), [11] (filled squares), [12] (filled triangles), [13] (open circles), [14] (open squares), and [15] (stars).…”

General study of superscaling in quasielastic(e,e')and(ν,μ

“…In Fig. 4, we compare data [49][50][51][52][53][54] with the results corresponding to the RIA-RMF approach with CC1 and CC2 at very different kinematics. As a general rule, we conclude that CC1 tends to overpredict data whereas the reverse applies to CC2.…”

Superscaling of non-quasielastic electron-nucleus scattering

“…[7], and focusing on scaling of the first kind, we have considered all available high-quality data of inelastic electron scattering cross sections on 12 C [33][34][35][36][37][38][39][40][41][42]. The functions f non-QE we obtain are shown in Fig.…”