The electromagnetic longitudinal and transverse inclusive responses for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, and ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ are analyzed using the concept of y scaling. The longitudinal, $F_L$, and transverse, $F_T$, scaling functions are defined, and their experimental values are obtained and compared with the predictions of two theoretical approaches. The first one, based upon the impulse approximation, Hartree-Fock-type wave functions for finite nuclei, and final state interaction treated by complex optical potentials, yields a reasonable interpretation of $F_L$ but cannot predict the experimental splitting between $F_L$ and $F_T$. The second approach, based on an infinite nuclear matter model, quantitatively reproduces the experimental splitting when the spin and isospin dependence of the effective particle-hole interaction is properly taken into account. The effects of ρ-meson exchange and Δ-hole intermediate states on the scaling functions are also analyzed.

• Received 7 November 1988

DOI:https://doi.org/10.1103/PhysRevC.39.1425