def _photon_integrand(self, x, Egamma):
        """
        Integrand of Eq. 72
        """
        try:
            return (
                self._sigma_inel(Egamma / x)
                * self._particle_distribution((Egamma / x))
                * self._Fgamma(x, Egamma / x)
                / x
            )
        except ZeroDivisionError:
            return np.nan
Integrand of Eq. 72