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// Bose-Einstein.h is a part of the PYTHIA event generator.
// Copyright (C) 2012 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.
// This file contains the classes to handle Bose-Einstein effects.
// BoseEinsteinHadron: simple working container for particle momenta.
// BoseEinstein: main class to perform the task.
#ifndef Pythia8_BoseEinstein_H
#define Pythia8_BoseEinstein_H
#include "Basics.h"
#include "Event.h"
#include "ParticleData.h"
#include "PythiaStdlib.h"
#include "Settings.h"
namespace Pythia8 {
//==========================================================================
// The BoseEinsteinHadron class is a simple container for studied hadrons.
class BoseEinsteinHadron {
public:
// Constructors.
BoseEinsteinHadron() : id(0), iPos(0), p(0.), pShift(0.), pComp(0.),
m2(0.) {}
BoseEinsteinHadron(int idIn, int iPosIn, Vec4 pIn, double mIn) :
id(idIn), iPos(iPosIn), p(pIn), pShift(0.), pComp(0.) {m2 = mIn*mIn;}
// Information on hadron - all public.
int id, iPos;
Vec4 p, pShift, pComp;
double m2;
};
//==========================================================================
// The BoseEinstein class shifts the momenta of identical particles relative
// to each other, to simulate Bose-Einstein effects to some approximation.
class BoseEinstein {
public:
// Constructor.
BoseEinstein() {}
// Find settings. Precalculate table used to find momentum shifts.
bool init(Info* infoPtrIn, Settings& settings, ParticleData& particleData);
// Perform Bose-Einstein corrections on an event.
bool shiftEvent( Event& event);
private:
// Constants: could only be changed in the code itself.
static const int IDHADRON[9], ITABLE[9], NCOMPSTEP;
static const double STEPSIZE, Q2MIN, COMPRELERR, COMPFACMAX;
// Initialization data, read from Settings.
bool doPion, doKaon, doEta;
double lambda, QRef;
// Pointer to various information on the generation.
Info* infoPtr;
// Table of momentum shifts for different hadron species.
int nStep[4], nStep3[4], nStored[10];
double QRef2, QRef3, R2Ref, R2Ref2, R2Ref3, mHadron[9],
mPair[4], m2Pair[4], deltaQ[4], deltaQ3[4], maxQ[4], maxQ3[4];
double shift[4][200], shift3[4][200];
// Vector of hadrons to study.
vector<BoseEinsteinHadron> hadronBE;
// Calculate shift and (unnormalized) compensation for pair.
void shiftPair(int i1, int i2, int iHad);
};
//==========================================================================
} // end namespace Pythia8
#endif // Pythia8_BoseEinstein_H
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