RooBreitWigner.cxx

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/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitModels                                                     *
 * @(#)root/roofit:$Id$
 * Authors:                                                                  *
 *   AS, Abi Soffer, Colorado State University, abi@slac.stanford.edu        *
 *   TS, Thomas Schietinger, SLAC, schieti@slac.stanford.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          Colorado State University                        *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/
 
/** \class RooBreitWigner
    \ingroup Roofit
 
Class RooBreitWigner is a RooAbsPdf implementation
that models a non-relativistic Breit-Wigner shape
**/
 
#include <cmath>
 
#include "RooBreitWigner.h"
#include "RooRealVar.h"
#include "RooHelpers.h"
#include "RooBatchCompute.h"
 
 
////////////////////////////////////////////////////////////////////////////////
 
RooBreitWigner::RooBreitWigner(const char *name, const char *title,
          RooAbsReal& _x, RooAbsReal& _mean,
          RooAbsReal& _width) :
  RooAbsPdf(name,title),
  x("x","Dependent",this,_x),
  mean("mean","Mean",this,_mean),
  width("width","Width",this,_width)
{
   RooHelpers::checkRangeOfParameters(this, {&_width}, 0.);
}
 
////////////////////////////////////////////////////////////////////////////////
 
RooBreitWigner::RooBreitWigner(const RooBreitWigner& other, const char* name) :
  RooAbsPdf(other,name), x("x",this,other.x), mean("mean",this,other.mean),
  width("width",this,other.width)
{
}
 
////////////////////////////////////////////////////////////////////////////////
 
double RooBreitWigner::evaluate() const
{
  double arg= x - mean;
  return 1. / (arg*arg + 0.25*width*width);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Compute multiple values of BreitWigner distribution.
void RooBreitWigner::doEval(RooFit::EvalContext & ctx) const
{
  RooBatchCompute::compute(ctx.config(this), RooBatchCompute::BreitWigner, ctx.output(), {ctx.at(x), ctx.at(mean), ctx.at(width)});
}
 
////////////////////////////////////////////////////////////////////////////////
 
Int_t RooBreitWigner::getAnalyticalIntegral(RooArgSet& allVars, RooArgSet& analVars, const char* /*rangeName*/) const
{
  if (matchArgs(allVars,analVars,x)) return 1 ;
  return 0 ;
}
 
////////////////////////////////////////////////////////////////////////////////
 
double RooBreitWigner::analyticalIntegral(Int_t code, const char* rangeName) const
{
  switch(code) {
  case 1:
    {
      double c = 2./width;
      return c*(atan(c*(x.max(rangeName)-mean)) - atan(c*(x.min(rangeName)-mean)));
    }
  }
 
  assert(0) ;
  return 0 ;
}