///////////////////////////////////////////////////////////////////////////////
// set PYTHIA to generate exclusive Z/gamma*->e e decay
///////////////////////////////////////////////////////////////////////////////
void  zee() {
  TG3Pythia6* py = TG3Pythia6::Instance();
//-----------------------------------------------------------------------------
// process 1 : ppbar --> Z/gamma*
//-----------------------------------------------------------------------------
  py->SetMSEL(0);
  py->SetMSUB(1,1);
//-----------------------------------------------------------------------------
// now turn off all the channels except Z->e e
// first decay channel: 174, Z->e e: #182
//-----------------------------------------------------------------------------
  int nch = py->NDecayChannels("Z0");

  for (int i=0; i<nch; i++) {
    int channel = 174+i;
    int code = py->GetMDME(channel,1);
    if (code > 0) {
      py->SetMDME(channel,1,0);
    }
  }
  py->SetMDME(182,1,1);
  py->PrintDecayChannels("Z0");
//-----------------------------------------------------------------------------
//  lower bound on the M(ee) 
//-----------------------------------------------------------------------------
  py->SetCKIN(1,30.);
}