///////////////////////////////////////////////////////////////////////////////
// set PYTHIA to generate exclusive W->e nu decay
///////////////////////////////////////////////////////////////////////////////
void  wmunu() {
  TG3Pythia6* py = TG3Pythia6::Instance();

  py->SetMSEL(0);
  py->SetMSUB(2,1);
//-----------------------------------------------------------------------------
// now turn off all the channels except W->e nu
// first decay channel: 190, W->e nu: #206
//-----------------------------------------------------------------------------
  int nch = py->NDecayChannels("W+");

  for (int i=0; i<nch; i++) {
    int code = py->GetMDME(190+i,1);
    if (code > 0) {
      py->SetMDME(190+i,1,0);
    }
  }
  py->SetMDME(207,1,1);
  py->PrintDecayChannels("W+");
}