Deep-inelastic electron scattering from 40 Ca, 48 Ca, and 56 Fe has been measured at 60°, 90°, and 140° and at inelasticities up to and including the A (3, 3) region. Longitudinal response functions in the momentum interval 300 MeV/c < |q| < 600 MeV/c were extracted. The experimental Coulomb sum rule is observed between the two calcium isotopes.
Deep-inelastic inclusive electron-scattering cross sections from 40 Ca, 48 Ca, and 56 Fe have been measured at 60°, 90°, and 140° and at energy transfers including the A(3,3) region. The transverse response function in the momentum interval 300 MeV/c < |q| < 600 MeV/c was extracted by the Rosenbluth prescription. Different theoretical approaches to the quasielastic region are compared to the data. A mass-number scaling is observed.PACS numbers: 25.30.Fj At energies above giant resonances, the inelastic electron-scattering cross section can be divided into three regions. First, there is the quasielastic region which appears as a broad peak, in which the dominant process is direct ejection of one bound nucleon from the nucleus through elastic scattering. Second, as the energy transfer becomes larger than the pion mass, it becomes possible to produce real pions and the A (3,3) resonance gives rise to a second large and broad peak. Finally, between these two peaks there iswhere R L and R T are the longitudinal and transverse response functions, M is the four-momentum transfer, a) the energy transfer, q the three-momentum transfer, E t the incident energy, 0 the laboratory scattering angle, and a the fine-structure constant. It is known 1 ' 2 that nuclear structure and dynamic effects, such as meson exchange currents and the A(3,3) resonance, contribute differently in the two response functions and thus a selective study of these processes can be made after their separation from the total response function. A strong constraint on the different theoretical approaches has been provided by recent experimental results. 3 " 6 However, data at large momentum transfers were needed for a more consistent and complete interpretation of these processes. a dip, which is dominated by direct ejection of two nucleons from the nucleus via the two-body currents. It should be pointed out that such divisions are somewhat arbitrary in that these processes may tend to overlap over a large range of energy transfer.New theoretical interest in deep-inelastic electron scattering on nuclei arises from the ability to separate experimentally the total response function into its transverse and longitudinal parts. If the one-photon exchange process is assumed, the inclusive differential cross section takes the following form:In this Letter we present results from deep-inelastic (e,e') measurements on 40 Ca, 48 Ca, and 56 Fe performed at the Saclay linear accelerator. In order to separate the transverse response function according to the Rosenbluth prescription, data were collected at incident energies ranging from 120 to 695 MeV and at three scattering angles: 60°, 90°, and 140°. The experimental procedure has been described in detail elsewhere. 5 ' 7,8 Although the maximum energy available at the linac (700 MeV) allowed us to cover the A (3,3) peak when measuring the total response function, the separation only goes slightly beyond the dip region. The reason is that the minimum scattered energy accessible at back-1233
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