Electromagnetic Response of C 12 : A First-Principles Calculation

The longitudinal and transverse electromagnetic response functions of 12C are computed in a “first-principles” Green’s function Monte Carlo calculation, based on realistic two- and three-nucleon interactions and associated one- and two-body currents. Here we find excellent agreement between theory and experiment and, in particular, no evidence for the quenching of the measured versus calculated longitudinal response. This is further corroborated by a reanalysis of the Coulomb sum rule, in which the contributions from the low-lying Jπ = 2+, 0$+\atop{2}$ (Hoyle), and 4+ states in 12C are accounted for explicitly in evaluating the total inelastic strength.