EvtBCSFF.cpp

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#include "EvtGenModels/EvtBCSFF.hh"

#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtReport.hh"

#include <iostream>
#include <math.h>
#include <stdlib.h>
#include <string>

using namespace std;

EvtBCSFF::EvtBCSFF( int idS, int fit )
{
    idScalar = idS;
    whichfit = fit;
    MBc = EvtPDL::getMeanMass( EvtPDL::getId( "B_c+" ) );
    MD0 = EvtPDL::getMeanMass( EvtPDL::getId( "D0" ) );
    return;
}

void EvtBCSFF::getscalarff( EvtId /*p*/, EvtId /*d*/, double t, double /*mass*/,
                            double* fpf, double* f0f )
{
    double q2 = t;

    if ( whichfit == 0 ) {
        *fpf = 1;
        *f0f = 0;
        return;
    }

    if ( idScalar == EvtPDL::getId( "chi_c0" ).getId() ) {    // Bc -> chi_c0
        if ( whichfit == 3 ) {    // FF from Wang et al 10.1103/PhysRevD.79.114018
            double ratio = q2 / ( MBc * MBc );

            double fpf_0 = 0.47;
            double fpf_c1 = 2.03;
            double fpf_c2 = 0.43;

            double f0f_0 = 0.47;
            double f0f_c1 = -0.45;
            double f0f_c2 = -1.31;

            *fpf = fpf_0 * exp( fpf_c1 * ratio + fpf_c2 * ratio * ratio );
            *f0f = f0f_0 * exp( f0f_c1 * ratio + f0f_c2 * ratio * ratio );
            return;

        } else {
            EvtGenReport( EVTGEN_ERROR, "EvtBCSFF" )
                << "Must choose 0 (fpf = 1) or 3 (Wang).\n";
            ::abort();
        }
    } else if ( idScalar == EvtPDL::getId( "D0" ).getId() ||
                idScalar == EvtPDL::getId( "anti-D0" ).getId() ) {    // Bc -> D0
        if ( whichfit == 1 ) {    // FF from Kiselev:2002vz, tables III, IV
            double q2invmass = q2 / ( MBc * MBc - MD0 * MD0 );
            double den = 1 - q2 / ( 5.0 * 5.0 );
            if ( fabs( den ) < 1e-10 ) {
                *fpf = 0;
                *f0f = 0;
            } else {
                double fPlus = 0.32 / den;
                double fMinus = -0.34 / den;
                *fpf = fPlus;
                *f0f = q2invmass * fMinus + fPlus;
            }
        } else if ( whichfit == 2 ) {    // FF from Ebert:2003cn, Fig 9
            double ratio = q2 / MBc / MBc;
            double const fPlus_0 = 0.143, fPlus_a = 0.7, fPlus_b = 2.13;
            double const f0_0 = 0.136, f0_a = 1.63, f0_b = -0.139;
            *fpf = fPlus_0 / ( 1 - fPlus_a * ratio - fPlus_b * ratio * ratio );
            *f0f = f0_0 / ( 1 - f0_a * ratio - f0_b * ratio * ratio );
            return;
        } else {
            EvtGenReport( EVTGEN_ERROR, "EvtBCSFF" )
                << "Should choose 1 (Kiselev:2002vz) or 2 (Ebert:2003cn).\n";
        }
    } else {
        EvtGenReport( EVTGEN_ERROR, "EvtBCSFF" )
            << "Only chi_c0 and D0/anti-D0 implemented.\n";
        ::abort();
    }
}

void EvtBCSFF::getvectorff( EvtId, EvtId, double, double, double*, double*,
                            double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getvectorff in EvtBCSFF.\n";
    ::abort();
}

void EvtBCSFF::gettensorff( EvtId /*p*/, EvtId /*d*/, double /*t*/,
                            double /*mass*/, double*, double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :gettensorff in EvtBCSFF.\n";
    ::abort();
}

void EvtBCSFF::getbaryonff( EvtId, EvtId, double, double, double*, double*,
                            double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getbaryonff in EvtBCSFF.\n";
    ::abort();
}

void EvtBCSFF::getdiracff( EvtId, EvtId, double, double, double*, double*,
                           double*, double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getdiracff in EvtBCSFF.\n";
    ::abort();
}

void EvtBCSFF::getraritaff( EvtId, EvtId, double, double, double*, double*,
                            double*, double*, double*, double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getraritaff in EvtBCSFF.\n";
    ::abort();
}