Hi,
Thank you for the code. But I really do not understand completely what you would like to to.
Your function Sigma calls Integrand which seems to try to compute an integral between 1 and + infinity of the function f1(x, parameters). But you do not pass the parameters from Sigma to Integrand.
Can you maybe explains in English or Math formula (even better) what you would like to do ?
One more comment, I would not mix floating precision with double. Just use double everywhere instead of float.
Lorenzo