EvtDalitzFlatPdf.cpp

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#include "EvtGenBase/EvtDalitzFlatPdf.hh"

#include "EvtGenBase/EvtPatches.hh"

EvtDalitzFlatPdf::EvtDalitzFlatPdf( const EvtDalitzPlot& dp ) :
    EvtPdf<EvtDalitzPoint>(), _dp( dp )
{
}

EvtDalitzFlatPdf::EvtDalitzFlatPdf( const EvtDalitzFlatPdf& other ) :
    EvtPdf<EvtDalitzPoint>( other ), _dp( other._dp )
{
}

EvtPdf<EvtDalitzPoint>* EvtDalitzFlatPdf::clone() const
{
    return new EvtDalitzFlatPdf( *this );
}

double EvtDalitzFlatPdf::pdf( const EvtDalitzPoint& ) const
{
    return 1.;
}

EvtValError EvtDalitzFlatPdf::compute_integral( int N ) const
{
    return EvtValError( _dp.getArea( N ), 0. );
}

EvtDalitzPoint EvtDalitzFlatPdf::randomPoint()
{
    // To obtain a uniform distribution generate
    // in terms of q's. Generate in a box that circumscribes the
    // Dalitz plot. Accept points inside. If there are two
    // many unsuccessful attempts it's a hint that the Dalitz plot
    // area is tiny compared to the box. It's a pathological
    // case. Abort.

    EvtCyclic3::Pair pair1 = EvtCyclic3::BC;
    EvtCyclic3::Pair pair2 = EvtCyclic3::CA;

    int n = 0;
    int maxTries = 1000;
    while ( n++ < maxTries ) {
        double q1 = EvtRandom::Flat( _dp.qAbsMin( pair1 ), _dp.qAbsMax( pair2 ) );
        double q2 = EvtRandom::Flat( _dp.qAbsMin( pair2 ), _dp.qAbsMax( pair2 ) );

        EvtDalitzCoord point( pair1, q1, pair2, q2 );
        EvtDalitzPoint x( _dp, point );

        if ( x.isValid() )
            return x;
    }

    printf( "No point generated for dalitz plot after %d tries\n", maxTries );
    return EvtDalitzPoint();
}