\begin{equation}
\lgg =2z\int\limits_{z^2/y_{max}}^{y_{max}}\frac{dy}{y}\left(
\frac{1}{{\sigma}_c}\frac{d{\sigma}_c(y)}{dy}\right)\left(\frac{1}
{\tilde{\sigma}_c}\frac{d\tilde{\sigma}_c(z^2/y)}{d(z^2/y)}\right)
\label{lumi_formel}
\end{equation}
