EvtBtoXsgammaFlatEnergy.cpp

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#include "EvtGenModels/EvtBtoXsgammaFlatEnergy.hh"

#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtReport.hh"

#include "EvtGenModels/EvtBtoXsgamma.hh"

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

void EvtBtoXsgammaFlatEnergy::init( int nArg, double* args )
{
    if ( ( nArg ) > 3 || ( nArg > 1 && nArg < 3 ) ) {
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "EvtBtoXsgamma generator model "
            << "EvtBtoXsgammaFlatEnergy expected "
            << "either 1(default config) or two arguments but found: " << nArg
            << endl;
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "Will terminate execution!" << endl;
        ::abort();
    }
    _mB0 = 5.2794;
    double mPi = 0.140;
    double mK = 0.494;
    if ( nArg == 1 ) {
        _eMin = 1.7;
        //Invariant mass of Xsd must be greater the m_pi+m_K leads to
        //Egamma < (m_B**2-(m_pi+m_k)**2)/(2m_B)
        _eMax = ( pow( _mB0, 2 ) - pow( mPi + mK, 2 ) ) / ( 2.0 * _mB0 );
    } else {
        _eMin = args[1];
        _eMax = args[2];
    }
    if ( _eMax > ( pow( _mB0, 2 ) - pow( mPi + mK, 2 ) ) / ( 2.0 * _mB0 ) ) {
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "Emax greater than Kinematic limit" << endl;
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "Reset to the kinematic limit" << endl;
        EvtGenReport( EVTGEN_ERROR, "EvtGen" )
            << "(m_B**2-(m_pi+m_k)**2)/(2m_B)" << endl;
        _eMax = ( pow( _mB0, 2 ) - pow( mPi + mK, 2 ) ) / ( 2.0 * _mB0 );
    }
    _eRange = _eMax - _eMin;
}

double EvtBtoXsgammaFlatEnergy::GetMass( int /*Xscode*/ )
{
    double eGamma = EvtRandom::Flat( _eRange ) + _eMin;
    double mH = sqrt( pow( _mB0, 2 ) - 2.0 * _mB0 * eGamma );
    return mH;
}