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BoseEinstein.h
1 // Bose-Einstein.h is a part of the PYTHIA event generator.
2 // Copyright (C) 2018 Torbjorn Sjostrand.
3 // PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
4 // Please respect the MCnet Guidelines, see GUIDELINES for details.
5 
6 // This file contains the classes to handle Bose-Einstein effects.
7 // BoseEinsteinHadron: simple working container for particle momenta.
8 // BoseEinstein: main class to perform the task.
9 
10 #ifndef Pythia8_BoseEinstein_H
11 #define Pythia8_BoseEinstein_H
12 
13 #include "Pythia8/Basics.h"
14 #include "Pythia8/Event.h"
15 #include "Pythia8/ParticleData.h"
16 #include "Pythia8/PythiaStdlib.h"
17 #include "Pythia8/Settings.h"
18 
19 namespace Pythia8 {
20 
21 //==========================================================================
22 
23 // The BoseEinsteinHadron class is a simple container for studied hadrons.
24 
25 class BoseEinsteinHadron {
26 
27 public:
28 
29  // Constructors.
30  BoseEinsteinHadron() : id(0), iPos(0), p(0.), pShift(0.), pComp(0.),
31  m2(0.) {}
32  BoseEinsteinHadron(int idIn, int iPosIn, Vec4 pIn, double mIn) :
33  id(idIn), iPos(iPosIn), p(pIn), pShift(0.), pComp(0.) {m2 = mIn*mIn;}
34 
35  // Information on hadron - all public.
36  int id, iPos;
37  Vec4 p, pShift, pComp;
38  double m2;
39 
40 };
41 
42 //==========================================================================
43 
44 // The BoseEinstein class shifts the momenta of identical particles relative
45 // to each other, to simulate Bose-Einstein effects to some approximation.
46 
47 class BoseEinstein {
48 
49 public:
50 
51  // Constructor.
52  BoseEinstein() {}
53 
54  // Find settings. Precalculate table used to find momentum shifts.
55  bool init(Info* infoPtrIn, Settings& settings, ParticleData& particleData);
56 
57  // Perform Bose-Einstein corrections on an event.
58  bool shiftEvent( Event& event);
59 
60 private:
61 
62  // Constants: could only be changed in the code itself.
63  static const int IDHADRON[9], ITABLE[9], NCOMPSTEP;
64  static const double STEPSIZE, Q2MIN, COMPRELERR, COMPFACMAX;
65 
66  // Initialization data, read from Settings.
67  bool doPion, doKaon, doEta;
68  double lambda, QRef;
69 
70  // Pointer to various information on the generation.
71  Info* infoPtr;
72 
73  // Table of momentum shifts for different hadron species.
74  int nStep[4], nStep3[4], nStored[10];
75  double QRef2, QRef3, R2Ref, R2Ref2, R2Ref3, mHadron[9],
76  mPair[4], m2Pair[4], deltaQ[4], deltaQ3[4], maxQ[4], maxQ3[4];
77  double shift[4][200], shift3[4][200];
78 
79  // Vector of hadrons to study.
80  vector<BoseEinsteinHadron> hadronBE;
81 
82  // Calculate shift and (unnormalized) compensation for pair.
83  void shiftPair(int i1, int i2, int iHad);
84 
85 };
86 
87 //==========================================================================
88 
89 } // end namespace Pythia8
90 
91 #endif // Pythia8_BoseEinstein_H
Definition: AgUStep.h:26