Gamma emission from the interaction between cosmic rays and molecular cloud

$$\begin{split}  \Phi_{\gamma} = & \frac{1}{4\pi d^2} \int dE'{ [\frac{4\pi}{c} \frac{dN}{dE'}(E')] *V} [ \frac{M_{mc}}{Vm_p}] \frac{d\sigma}{dE}(E,E')  c \\  = & \frac{M_{mc}}{d^2m_p} \int dE' \frac{dN}{dE'}(E') \frac{d\sigma}{dE}(E,E') \end{split}$$

$$N \propto exp(-\frac{r^2}{4Dt})$$

$E_{\gamma} \sim 10\%E_p$