Corrected mass range in Pythia. Fixes LHCBGAUSS-1628
Port the merging of branch 'LHCBGAUSS-1628-Fix.Sim09' into 'Sim09-upgrade'
Correspond to merge request !435 (merged) for 'Sim09'
(cherry picked from commit 50686165)
8ad12f61 Corrected mass range in Pythia. Fixes LHCBGAUSS-1628