EXACT HE-4 SPECTRAL-FUNCTION IN A SEMIREALISTIC NN POTENTIAL MODEL

The spectral function of He-4 is calculated with the Lorentz integral transform method in a large energy and momentum range. The excitation spectrum of the residual 3N system is fully taken into account. The ob tained spectral function is used to calculate the quasielastic longitu dinal (e,e') response R-L Of 4He for q = 300, 400, and 500 MeV/c. Comp arison with the exact R-L shows a rather sizable disagreement except i n the quasielastic peak, where the differences reduce to about 10% at q=500 MeV/c. It is shown as well that very simple momentum distributio n approximations for the spectral function provide almost the same res ults for R-L as the exact spectral function.