Light scattering spectrum ofHe4forT>~Tλin three dimensions

The field-theoretic renormalization-group formalism is used to calculate the light scattering spectrum of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ for $T>~T_{\lambda }$ self-consistently to second order in the loop expansion. It is shown that owing to the finite wave vector of the experiments the system never comes close to its fixed point (even for $T=T_{\lambda }$), and transients must be included consistently to explain the data. Previous explanations of the absence of temperature dependence of the linewidth, in terms of the effect of the weak-scaling fixed point, are shown to be incorrect.