RooCBExGaussShape.cc

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#include "PhysicsTools/TagAndProbe/interface/RooCBExGaussShape.h" 

ClassImp(RooCBExGaussShape) 

 RooCBExGaussShape::RooCBExGaussShape(const char *name, const char *title, 
                      RooAbsReal& _m,
                      RooAbsReal& _m0,
                      RooAbsReal& _sigma,
                      RooAbsReal& _alpha,
                      RooAbsReal& _n,
                      RooAbsReal& _sigma_2,
                      RooAbsReal& _frac
) :
   RooAbsPdf(name,title), 
   m("m","m",this,_m),
   m0(" m0"," m0",this,_m0),
   sigma(" sigma"," sigma",this,_sigma),
   alpha(" alpha"," alpha",this,_alpha),
   n(" n"," n",this,_n),
   sigma_2(" sigma_2"," sigma_2",this,_sigma_2),
   frac(" frac"," frac",this,_frac) 
{ }

RooCBExGaussShape::RooCBExGaussShape(const RooCBExGaussShape& other, const char* name):
  RooAbsPdf(other,name), 
  m("m",this,other.m),
  m0(" m0",this,other. m0),
  sigma(" sigma",this,other. sigma),
  alpha(" alpha",this,other. alpha),
  n(" n",this,other. n),
  sigma_2(" sigma_2",this,other. sigma_2),
  frac(" frac",this,other. frac)
{ }


 Double_t RooCBExGaussShape::evaluate() const 
 { 
   Double_t rval=0;

   Double_t t = (m-m0)/sigma;
   Double_t t0 = (m-m0)/sigma_2;
   if (alpha < 0){ 
     t = -t;
     t0 = -t0;
   }

   Double_t absAlpha = fabs((Double_t)alpha);

   if (t >= -absAlpha) {
     rval= frac*exp(-0.5*t*t) + (1.0-frac)*exp(-0.5*t0*t0);
   }
   else {
     Double_t a =  TMath::Power(n/absAlpha,n)*exp(-0.5*absAlpha*absAlpha);
     Double_t b= n/absAlpha - absAlpha; 
     rval= a/TMath::Power(b - t, n);
   }

   //std::cout<<"RooCBExGaussShape: m, evaluate= "<<m<<", "<<rval<<std::endl;
   return rval;
 }