include/EvtGenBase/EvtDalitzResPdf.hh

0001
0002 /***********************************************************************
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0020
0021 #ifndef EVT_DALITZ_RES_PDF_HH
0022 #define EVT_DALITZ_RES_PDF_HH
0023
0024 #include "EvtGenBase/EvtCyclic3.hh"
0025 #include "EvtGenBase/EvtDalitzPoint.hh"
0026 #include "EvtGenBase/EvtPdf.hh"
0027
0028 /*
0029  * Pole compensating function for terms that exibit a resonant structure
0030  * in one dimension only.
0031  *
0032  * f =  1    g*m0
0033  *     --  ------------------
0034  *     pi  (q-q0)^2 + g^2m0^2
0035  *
0036  * m is the mass of the resonance, g is its width. The approximation works well for a narrow
0037  * resonance. It is also readily integrable over the Dalitz plot coordinate to produce
0038  *
0039  * Int = 1/pi atan((q-q0)/(g*m0))
0040  */
0041
0042 class EvtDalitzResPdf : public EvtPdf<EvtDalitzPoint> {
0043   public:
0044     EvtDalitzResPdf( const EvtDalitzPlot& dp, double m0, double g0,
0045                      EvtCyclic3::Pair pairRes );
0046
0047     EvtPdf<EvtDalitzPoint>* clone() const override
0048     {
0049         return new EvtDalitzResPdf( *this );
0050     }
0051
0052     using EvtPdf<EvtDalitzPoint>::compute_integral;
0053     EvtValError compute_integral( int N ) const override;
0054     EvtDalitzPoint randomPoint() override;
0055     double pdfMaxValue() const;
0056
0057   protected:
0058     double pdf( const EvtDalitzPoint& ) const override;
0059
0060   private:
0061     EvtDalitzPlot _dp;
0062     double _m0;                // mass
0063     double _g0;                // width
0064     EvtCyclic3::Pair _pair;    // resonant pair
0065 };
0066
0067 #endif