Fix sampling in SimpleDDCS model
The sampling must take into account the log-log shape when sampling from the distribution. The SDCS slope part is only linear in log-log shape and hence sampling must be adjusted.
Reference:
This plateau-slope shape can be parametrized by the four parameters sigmaP (the plateau value of the SDCS), sigmaS (the SDCS value at the end of the slope), EP (the energy where the plateau ends and the slope starts) and ES (the energy where the slope ends); the plateau is assumed to start at E = 0
. Note that this plateau-slope shape occurs in a log-log form and therefore the underlying distribution for the slope part is of the form
\frac{d\sigma}{dE}^{slope} = \frac{\sigma_P}{E_P^a} \cdot E^a , a = \frac{\log\left( \sigma_S / \sigma_P \right)}{\log\left( E_S / E_P \right)}