[Rivet] Pythia+PU+Rivet problem

[Tomasz Fruboes]

Dear Experts,

  in our rivet (1.82) analysys I'm trying to include pileup. Pileup is 
added on generator level by pythia6 using following settings:

             'MSTP(131)=1
             'MSTP(132)=3
             'MSTP(133)=1
             'PARP(131)=0.15

Above gives n=10 PU interactions on average. In every 1 out of ~300 
events I'm getting following exception

A std::exception was thrown.
Particle ID '1' not known.

(where ID can be 2 or 3 as well).

I have added try/catch block in order to handle this (see [1] below). 
Could you comment if this is a safe workaround? Or maybe there is a 
better solution?

  Thank you,
   Tomasz Fruboes


[1] Source code of our rivet wrapper:

https://github.com/cms-sw/cmssw/blob/CMSSW_7_1_X/GeneratorInterface/RivetInterface/plugins/RivetAnalyzer.cc

Line ~120 was changed to
   //run the analysis
   try {
       _analysisHandler.analyze(*myGenEvent);
   } catch (...) {
         std::cout << "Exception caught...\n" ;
   }