EvtPFermi.cc

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//-----------------------------------------------------------------------
// File and Version Information:
//
// Copyright Information: See EvtGen/COPYRIGHT
//
//
// Description:
//   F(k+) = N (1-x)^a exp((1+a)x) ,x=k+/(mB-mb)
//   the fermi motion distribution according to
//   hep-ph/9905351 v2
//
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Author List:
//      Sven Menke
//
//-----------------------------------------------------------------------
//-----------------------
// This Class's Header --
//-----------------------
#include "EvtPFermi.hh"
#include "../EvtGenBase/EvtPatches.hh"
 
//---------------
// C Headers --
//---------------
#include <math.h>
 
//----------------
// Constructors --
//----------------
 
EvtPFermi::EvtPFermi( const double& a, const double& mB, const double& mb ) {
  _a  = a;
  _mb = mb;
  _mB = mB;
}
 
//--------------
// Destructor --
//--------------
 
EvtPFermi::~EvtPFermi() {}
 
//-----------
// Methods --
//-----------
 
double EvtPFermi::getFPFermi( const double& kplus ) {
  double FKplus;
  double x = kplus / ( _mB - _mb );
 
  if ( x >= 1 ) return 0;
  if ( kplus <= -_mb ) return 0;
 
  FKplus = pow( 1 - x, _a ) * exp( ( 1 + _a ) * x );
 
  return FKplus;
}