Double_t tpileup_p2e(Double_t *t, Double_t *par) // p2e pileup pdf
 { 
   double yield = 0.;
   double tau_pi = 26.03;
   double tau_mu = 2197.;
   double pg_start = -69.70; // opening of PiGate
   double pg_close = 222.50; // closing of PiGate
   double T = 19.75;         // rf Period, ns
   double sigma = 1.;        // TDC resolution, ns

   if ( t[0] > pg_start && t[0] < pg_close ) {
     for (int n= -7; n<11; n++ ) {  // 5 pion lifetimes into past
       if ( t[0]>n*T )              // causality
         yield+ = exp( (-t[0] + n*T)/tau_pi); } // end for 
     return par[0]*yield; } // end if
   else if ( t[0] < pg_start && fabs(t[0] - pg_start )< 3*sigma ) {
     for (int n= -7; n<11; n++ ) {  // 5 pion lifetimes into past
       if ( t[0]>n*T )              // causality
         yield+ = exp( (-t[0] + n*T)/tau_pi); } // end for 
     yield = yield * exp( -0.5* (t[0]- pg_start)*(t[0]- pg_start)/(sigma*sigma) );
       return par[0]*yield; } // end else if
  else if ( t[0] > pg_close && fabs(t[0] - pg_close )< 3*sigma ) {
     for (int n= -7; n<11; n++ ) {  // 5 pion lifetimes into past
       if ( t[0]>n*T )              // causality
         yield+ = exp( (-t[0] + n*T)/tau_pi); } // end for 
     yield = yield * exp( -0.5* (t[0]- pg_close)*(t[0]- pg_close)/(sigma*sigma) );
       return par[0]*yield; } // end else if
   else 
     return yield;
 }