Inspecting the power of parton showering the generated events by   comparing the events generated in NLO+PS to NLO and NNLO without parton   shower in $e^+e^-$ at 91.2 GEV
  In this study we tried to emphasize the role parton shower plays in event generation, and in the physics of high energy event generation. We achieved this task by comparing the next-to-leading order and next-to-next-to-leading order results from EERAD3 with the next-to-leading order plus parton shower results from Vincia, and comparing both with real data. 
Hessamoddin Kaveh, Mohammad Ebrahim Zomorrodian
hep-ph