EvtDalitzResPdf.hh

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#ifndef EVT_DALITZ_RES_PDF_HH
#define EVT_DALITZ_RES_PDF_HH
 
#include "EvtGenBase/EvtCyclic3.hh"
#include "EvtGenBase/EvtDalitzPoint.hh"
#include "EvtGenBase/EvtPdf.hh"
 
/*
 * Pole compensating function for terms that exibit a resonant structure
 * in one dimension only.
 *
 * f =  1    g*m0
 *     --  ------------------
 *     pi  (q-q0)^2 + g^2m0^2
 *
 * m is the mass of the resonance, g is its width. The approximation works well for a narrow
 * resonance. It is also readily integrable over the Dalitz plot coordinate to produce
 *
 * Int = 1/pi atan((q-q0)/(g*m0))
 */
 
class EvtDalitzResPdf : public EvtPdf<EvtDalitzPoint> {
  public:
    EvtDalitzResPdf( const EvtDalitzPlot& dp, double m0, double g0,
                     EvtCyclic3::Pair pairRes );
 
    EvtPdf<EvtDalitzPoint>* clone() const override
    {
        return new EvtDalitzResPdf( *this );
    }
 
    using EvtPdf<EvtDalitzPoint>::compute_integral;
    EvtValError compute_integral( int N ) const override;
    EvtDalitzPoint randomPoint() override;
    double pdfMaxValue() const;
 
  protected:
    double pdf( const EvtDalitzPoint& ) const override;
 
  private:
    EvtDalitzPlot m_dp;
    double m_m0;                // mass
    double m_g0;                // width
    EvtCyclic3::Pair m_pair;    // resonant pair
};
 
#endif