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Herwig  7.1.5
Kinematics.h
1 // -*- C++ -*-
2 //
3 // Kinematics.h is a part of Herwig - A multi-purpose Monte Carlo event generator
4 // Copyright (C) 2002-2017 The Herwig Collaboration
5 //
6 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
7 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
8 //
9 //
10 #ifndef HERWIG_Kinematics_H
11 #define HERWIG_Kinematics_H
12 
13 // This is the declaration of the Kinematics class.
14 
15 #include <ThePEG/Config/ThePEG.h>
17 #include "ThePEG/Vectors/LorentzRotation.h"
18 #include "ThePEG/Repository/UseRandom.h"
19 #include <ThePEG/Vectors/Lorentz5Vector.h>
20 
21 namespace Herwig {
22 
23  using namespace ThePEG;
24 
33  namespace Kinematics {
34 
46  bool twoBodyDecay(const Lorentz5Momentum & p,
47  const Energy m1, const Energy m2,
48  const Axis & unitDir1,
49  Lorentz5Momentum & p1, Lorentz5Momentum & p2);
50 
54  inline Axis unitDirection(const double cosTheta, const double phi) {
55  return ( fabs( cosTheta ) <= 1.0 ?
56  Axis( cos(phi)*sqrt(1.0-cosTheta*cosTheta) ,
57  sin(phi)*sqrt(1.0-cosTheta*cosTheta) , cosTheta) : Axis() );
58  }
59 
71  inline bool twoBodyDecay(const Lorentz5Momentum & p,
72  const Energy m1, const Energy m2,
73  const double cosThetaStar1,
74  const double phiStar1,
75  Lorentz5Momentum & p1, Lorentz5Momentum & p2) {
76  return twoBodyDecay(p,m1,m2,unitDirection(cosThetaStar1,phiStar1),p1,p2);
77  }
78 
85  bool threeBodyDecay(Lorentz5Momentum p0, Lorentz5Momentum &p1,
86  Lorentz5Momentum &p2, Lorentz5Momentum &p3,
87  double (*fcn)(Energy2,Energy2,Energy2,InvEnergy4) = NULL);
88 
93  inline Energy pstarTwoBodyDecay(const Energy M,
94  const Energy m1, const Energy m2) {
95  return ( M > ZERO && m1 >=ZERO && m2 >= ZERO && M > m1+m2 ?
96  Energy(sqrt(( sqr(M) - sqr(m1+m2) )*( sqr(M) - sqr(m1-m2) ))
97  / (2.0*M) ) : ZERO);
98  }
99 
103  inline void generateAngles(double & ct, double & az) {
104  ct = UseRandom::rnd()*2.0 - 1.0; // Flat from -1..1
105  az = UseRandom::rnd()*Constants::twopi;
106  }
107  }
108 
109 }
110 
111 #endif /* HERWIG_Kinematics_H */
112 
void generateAngles(double &ct, double &az)
This just generates angles.
Definition: Kinematics.h:103
bool twoBodyDecay(const Lorentz5Momentum &p, const Energy m1, const Energy m2, const Axis &unitDir1, Lorentz5Momentum &p1, Lorentz5Momentum &p2)
Calculate the momenta for a two body decay The return value indicates success or failure.
double sqrt(int x)
static double rnd()
constexpr BinaryOpTraits< T, T >::MulT sqr(const T &x)
Energy pstarTwoBodyDecay(const Energy M, const Energy m1, const Energy m2)
For the two body decay M -> m1 + m2 it gives the module of the 3-momentum of the decay product in the...
Definition: Kinematics.h:93
Axis unitDirection(const double cosTheta, const double phi)
It returns the unit 3-vector with the given cosTheta and phi.
Definition: Kinematics.h:54
bool threeBodyDecay(Lorentz5Momentum p0, Lorentz5Momentum &p1, Lorentz5Momentum &p2, Lorentz5Momentum &p3, double(*fcn)(Energy2, Energy2, Energy2, InvEnergy4)=NULL)
As the name implies, this takes the momentum p0 and does a flat three body decay into p1...
-*- C++ -*-
constexpr ZeroUnit ZERO