_fPt = TF1 ("pTacceptance", "(1+TMath::Erf((x-[0])*[1]))*(1+TMath::Erf((x-[2])*[3]))/4",3, 123);
  _fPt.SetParameter(0, 22.4);
  _fPt.SetParameter(1, .0957);
  _fPt.SetParameter(2, -137.8);
  _fPt.SetParameter(3, 0.00609);

  _fLPt = TF1 ("LpTacceptance", "(1+TMath::Erf((x-[0])*[1]))*(1+TMath::Erf((x-[2])*[3]))/4",3, 123);
  _fLPt.SetParameter(0, 35.4);
  _fLPt.SetParameter(1, .08);
  _fLPt.SetParameter(2, -117.7);
  _fLPt.SetParameter(3, 0.00650);

  _fEta = TF1 ("etaAcceptance", "TMath::Max(0,(1-TMath::Erf((x-[0])*[1]))*0.5*[2]*(1+x*[3]+x**2*[4]+x**3*[5]))", 0, 2.9);
  _fEta.SetParameter(0, 2.56);
  _fEta.SetParameter(1, 5.23);
  _fEta.SetParameter(2, 0.912);
  _fEta.SetParameter(3, -0.0193);
  _fEta.SetParameter(4, 0.0238);
  _fEta.SetParameter(5, -0.02046);

  probability of jet selection:   _fPt.Eval (effPt) * _fEta..Eval (effPt);

  probability of jet satisfying the leading jet cut: _fLPt.Eval (effPt) * _fEta..Eval (effPt);