evt_dalitz.cc
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	/***********************************************************************
	* Copyright 1998-2020 CERN for the benefit of the EvtGen authors *
	* *
	* This file is part of EvtGen. *
	* *
	* EvtGen is free software: you can redistribute it and/or modify *
	* it under the terms of the GNU General Public License as published by *
	* the Free Software Foundation, either version 3 of the License, or *
	* (at your option) any later version. *
	* *
	* EvtGen is distributed in the hope that it will be useful, *
	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
	* GNU General Public License for more details. *
	* *
	* You should have received a copy of the GNU General Public License *
	* along with EvtGen. If not, see <https://www.gnu.org/licenses/>. *
	***********************************************************************/

	/*
	* Generate the kinematics of a Dalitz decay
	* according to a decay file.
	*/

	#include "EvtGen/EvtGen.hh"

	#include "EvtGenBase/EvtAbsRadCorr.hh"
	#include "EvtGenBase/EvtDecayBase.hh"
	#include "EvtGenBase/EvtMTRandomEngine.hh"
	#include "EvtGenBase/EvtPDL.hh"
	#include "EvtGenBase/EvtParticle.hh"
	#include "EvtGenBase/EvtParticleFactory.hh"
	#include "EvtGenBase/EvtRandom.hh"
	#include "EvtGenBase/EvtSimpleRandomEngine.hh"
	#include "EvtGenBase/EvtVector4R.hh"

	#include <fstream>
	#include <stdio.h>
	#include <unistd.h>

	#ifdef EVTGEN_EXTERNAL
	#include "EvtGenExternal/EvtExternalGenList.hh"
	#endif

	#include <cstdlib>
	#include <list>
	#include <string>

	using std::endl;
	using std::fstream;
	using std::ifstream;
	using std::ofstream;

	void usage( const char* cmd )
	{
	printf( "Usage: %s -d <decayfile> -m <mother> -n <nevents> -f <datfile> -r <rootfile>\n",
	cmd );
	}

	int main( int argc, char* argv[] )
	{
	std::string mother( "B+" );
	int N = 10;
	std::string datfile( "output.dat" );
	std::string decfile = ( "../DECAY.DEC" );

	// Get options

	extern char* optarg;
	int c;
	while ( ( c = getopt( argc, argv, "d:m:n:f:" ) ) != EOF ) {
	switch ( c ) {
	case 'm':
	mother = std::string( optarg );
	break;
	case 'n':
	N = atoi( optarg );
	break;
	case 'f':
	datfile = std::string( optarg );
	break;
	case 'd':
	decfile = std::string( optarg );
	break;
	}
	}

	// Initialize EvtGen

	// Define the random number generator
	EvtRandomEngine* eng = 0;

	#ifdef EVTGEN_CPP11
	// Use the Mersenne-Twister generator (C++11 only)
	eng = new EvtMTRandomEngine();
	#else
	eng = new EvtSimpleRandomEngine();
	#endif

	EvtRandom::setRandomEngine( eng );

	EvtAbsRadCorr* radCorrEngine = 0;
	std::list<EvtDecayBase*> extraModels;

	#ifdef EVTGEN_EXTERNAL
	bool convertPythiaCodes( false );
	bool useEvtGenRandom( true );
	EvtExternalGenList genList( convertPythiaCodes, "", "gamma", useEvtGenRandom );
	radCorrEngine = genList.getPhotosModel();
	extraModels = genList.getListOfModels();
	#endif

	EvtGen myGenerator( decfile.c_str(), "../evt.pdl", eng, radCorrEngine,
	&extraModels );

	// Initialize decay

	EvtId id = EvtPDL::getId( mother );

	// generate

	ofstream df( datfile.c_str() );

	int count = 1;
	do {
	EvtVector4R p_init( EvtPDL::getMass( id ), 0.0, 0.0, 0.0 );
	EvtParticle* root_part = EvtParticleFactory::particleFactory( id, p_init );
	root_part->setDiagonalSpinDensity();
	myGenerator.generateDecay( root_part );

	int nDaug = root_part->getNDaug();
	if ( nDaug == 3 ) {
	EvtVector4R p0 = root_part->getDaug( 0 )->getP4Lab();
	EvtVector4R p1 = root_part->getDaug( 1 )->getP4Lab();
	EvtVector4R p2 = root_part->getDaug( 2 )->getP4Lab();
	double qAB = ( p0 + p1 ).mass2();
	double qBC = ( p1 + p2 ).mass2();
	double qCA = ( p2 + p0 ).mass2();

	df << qAB << " " << qBC << " " << qCA << " " << endl;
	}

	root_part->deleteTree();

	} while ( count++ < N );

	delete eng;
	}

	// Macro for displaying resutls
	/*
	TTree* readTree(const char* file, int N)
	{
	double qAB,qBC,qCA;
	TTree* t = new TTree();
	t->Branch("qAB",&qAB,"qAB/D");
	t->Branch("qBC",&qBC,"qBC/D");
	t->Branch("qCA",&qCA,"qCA/D");

	ifstream f(file);

	int i=0;
	while(i < N) {
	i++;
	f >> qAB >> qBC >> qCA;
	t->Fill();
	}

	return t;
	}
	*/

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