// Breit-Wigner with m=110 GeV
Double_t bw(Double_t *x, Double_t *par) {
  return (0.5*par[0]*par[1]/TMath::Pi() / TMath::Max( 1.0e-10, (x[0]-110.0)*(x[0]-110.0) + 0.25*par[1]*par[1] ) );
}