Double_t tpileup_accid(Double_t *t, Double_t *par) // the simplest accidental pileup pdf, replaces tpileup_mich+tpileup_p2e
 { 
   double yield = 0.;
   double pg_start = -69.70; // opening of PiGate
   double pg_close = 222.50; // closing of PiGate
   double sigma = 1.;        // gate edge resolution, ns

   if ( t[0] > pg_start && t[0] < pg_close ) {
     yield = par [0]; 
     return yield; } // end if
   else if ( t[0] < pg_start && fabs( t[0] - pg_start )< 3*sigma ) {
     yield = par[0]*exp( -0.5*(t[0] - pg_start )*( t[0] - pg_start )/(sigma*sigma) );
     return yield; } // end else if
   else if ( t[0] > pg_close && fabs( t[0] - pg_close )< 3*sigma ) {
     yield = par[0]*exp( -0.5*(t[0] - pg_close )*( t[0] - pg_close )/(sigma*sigma) );
     return yield; } // end else if
   else 
     return yield;
 }