Final-state effects on superfluid 4He in the deep inelastic regime.

A study of final-state effects ~FSE! on the dynamic structure function of superfluid He in the GerschRodriguez formalism is presented. The main ingredients needed in the calculation are the momentum distribution and the semidiagonal two-body density matrix. The influence of these ground-state quantities on the FSE is analyzed. A variational form of r2 is used, even though simpler forms turn out to give accurate results if properly chosen. Comparison to the experimental response at high momentum transfer is performed. The predicted response is quite sensitive to slight variations on the value of the condensate fraction, the best agreement with experiment being obtained with n050.082. Sum rules of the FSE broadening function are also derived and commented. Finally, it is shown that Gersch-Rodriguez theory produces results as accurate as those coming from other more recent FSE theories.