EvtLb2plnuLQCDFF.cpp

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#include "EvtGenModels/EvtLb2plnuLQCDFF.hh"

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

#include <math.h>
#include <stdlib.h>
#include <string>
using std::endl;

void EvtLb2plnuLQCDFF::getdiracff( EvtId parent, EvtId daught, double q2,
                                   double /* mass */, double* f1, double* f2,
                                   double* f3, double* g1, double* g2, double* g3 )
{
    // Define Event IDs for Lb and p
    static EvtId LAMB = EvtPDL::getId( "Lambda_b0" );
    static EvtId LAMBB = EvtPDL::getId( "anti-Lambda_b0" );
    static EvtId PRO = EvtPDL::getId( "p+" );
    static EvtId PROB = EvtPDL::getId( "anti-p-" );

    if ( ( parent == LAMB && daught == PRO ) ||
         ( parent == LAMBB && daught == PROB ) ) {
        // Calculate Lb->p form factors based on LQCD predictions
        // Predictions taken from W. Detmold, C-J. Lin, S. Meinel and M.Wingate, arXiv:1306.0446 (2013)

        double MLamB = EvtPDL::getMass( parent );
        double MPro = EvtPDL::getMass( daught );
        double Y1 = 2.97;
        double X1 = 1.36;
        double Y2 = -0.28;
        double X2 = 0.81;
        double EnMn = ( MLamB * MLamB + MPro * MPro - q2 ) / ( 2.0 * MLamB ) -
                      MPro;
        double F1 = Y1 / ( ( X1 + EnMn ) * ( X1 + EnMn ) );
        double F2 = Y2 / ( ( X2 + EnMn ) * ( X2 + EnMn ) );
        double pi = atan( 1.0 ) * 4.0;
        double alphas = 0.214;
        double cv = 2.0 / 3.0 * alphas / pi;
        double cgam = 1.0 - ( alphas / pi ) * ( 4.0 / 3.0 );

        *f1 = cgam * ( F1 - F2 );
        *f2 = cv * F1 + ( 2.0 * cgam + cv ) * F2;
        *f3 = 0.0;
        *g1 = cgam * ( F1 + F2 );
        *g2 = -cv * F1 + ( 2.0 * cgam + cv ) * F2;
        *g3 = 0.0;

    } else {
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "Only Lb -> p transitions allowed in EvtLb2plnuLQCDFF.\n";
        ::abort();
    }

    return;
}

void EvtLb2plnuLQCDFF::getraritaff( EvtId, EvtId, double, double, double*,
                                    double*, double*, double*, double*, double*,
                                    double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getraritaff in EvtLb2plnuLQCDFF.\n";
    ::abort();
}

void EvtLb2plnuLQCDFF::getscalarff( EvtId, EvtId, double, double, double*,
                                    double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getscalarff in EvtLb2plnuLQCDFF.\n";
    ::abort();
}

void EvtLb2plnuLQCDFF::getvectorff( EvtId, EvtId, double, double, double*,
                                    double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getvectorff in EvtLb2plnuLQCDFF.\n";
    ::abort();
}

void EvtLb2plnuLQCDFF::gettensorff( EvtId, EvtId, double, double, double*,
                                    double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :gettensorff in EvtLb2plnuLQCDFF.\n";
    ::abort();
}

void EvtLb2plnuLQCDFF::getbaryonff( EvtId, EvtId, double, double, double*,
                                    double*, double*, double* )
{
    EvtGenReport( EVTGEN_ERROR, "EvtGen" )
        << "Not implemented :getbaryonff in EvtLb2plnuLQCDFF.\n";
    ::abort();
}