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G4INCL::EtaNToPiNChannel Class Reference

#include <G4INCLEtaNToPiNChannel.hh>

Inheritance diagram for G4INCL::EtaNToPiNChannel:
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Public Member Functions

 EtaNToPiNChannel (Particle *, Particle *)
 
virtual ~EtaNToPiNChannel ()
 
void fillFinalState (FinalState *fs)
 
- Public Member Functions inherited from G4INCL::IChannel
 IChannel ()
 
virtual ~IChannel ()
 
FinalState * getFinalState ()
 

Detailed Description

Definition at line 47 of file G4INCLEtaNToPiNChannel.hh.

Constructor & Destructor Documentation

G4INCL::EtaNToPiNChannel::EtaNToPiNChannel ( Particle *  p1,
Particle *  p2 
)

Definition at line 47 of file G4INCLEtaNToPiNChannel.cc.

48  : particle1(p1), particle2(p2)
49  {
50 
51  }
G4INCL::EtaNToPiNChannel::~EtaNToPiNChannel ( )
virtual

Definition at line 53 of file G4INCLEtaNToPiNChannel.cc.

53  {
54 
55  }

Member Function Documentation

void G4INCL::EtaNToPiNChannel::fillFinalState ( FinalState *  fs)
virtual

Implements G4INCL::IChannel.

Definition at line 57 of file G4INCLEtaNToPiNChannel.cc.

57  {
58  Particle * nucleon;
59  Particle * eta;
60  if(particle1->isNucleon()) {
61  nucleon = particle1;
62  eta = particle2;
63  } else {
64  nucleon = particle2;
65  eta = particle1;
66  }
67 
68  const G4double r2 = Random::shoot();
69  if (nucleon->getType() == Neutron) {
70  if (r2*3. < 2.) {
71  nucleon->setType(Proton);
72  eta->setType(PiMinus);
73  }
74  else {
75  nucleon->setType(Neutron);
76  eta->setType(PiZero);
77  }
78  }
79  else {
80  if (r2*3. < 2.) {
81  nucleon->setType(Neutron);
82  eta->setType(PiPlus);
83  }
84  else {
85  nucleon->setType(Proton);
86  eta->setType(PiZero);
87  }
88  }
89 
90  G4double sh=nucleon->getEnergy()+eta->getEnergy();
91  G4double mn=nucleon->getMass();
92  G4double me=eta->getMass();
93  G4double en=(sh*sh+mn*mn-me*me)/(2*sh);
94  nucleon->setEnergy(en);
95  G4double ee=std::sqrt(en*en-mn*mn+me*me);
96  eta->setEnergy(ee);
97  G4double pn=std::sqrt(en*en-mn*mn);
98 /* isotropy
99 
100  ThreeVector mom_nucleon = Random::normVector(pn);
101 
102  nucleon->setMomentum(mom_nucleon);
103  eta->setMomentum(-mom_nucleon);
104 */
105 
106 // real distribution (from PRC 78, 025204 (2008)) --- detailed balance from pi nucleon --> eta nucleon
107 
108 
109  G4double ECM=G4INCL::KinematicsUtils::totalEnergyInCM(particle1,particle2);
110 
111  const G4double pi=std::acos(-1.0);
112  G4double x1;
113  G4double u1;
114  G4double fteta;
115  G4double teta;
116  G4double fi;
117 
118  if (ECM < 1650.) {
119  // below 1650 MeV - angular distribution (x=cos(theta): ax^2+bx+c
120 
121  G4double f1= -0.0000288627*ECM*ECM+0.09155289*ECM-72.25436; // f(1) that is the maximum (fit on experimental data)
122  G4double b1=(f1-(f1/(1.5-0.5*std::pow((ECM-1580.)/95.,2))))/2.; // ideas: 1) f(-1)=0.5f(1); 2) "power term" flattens the distribution away from ECM=1580 MeV
123  G4double a1=2.5*b1; // minimum at cos(theta) = -0.2
124  G4double c1=f1-3.5*b1;
125 
126  G4double interg1=2.*a1/3. +2.*c1; // (integral to normalize)
127 
128  G4int passe1=0;
129  while (passe1==0) {
130  // Sample x from -1 to 1
131  x1=Random::shoot();
132  if (Random::shoot() > 0.5) x1=-x1;
133 
134  // Sample u from 0 to 1
135  u1=Random::shoot();
136  fteta=(a1*x1*x1+b1*x1+c1)/interg1;
137  // The condition
138  if (u1*f1/interg1 < fteta) {
139  teta=std::acos(x1);
140  passe1=1;
141  }
142  }
143  }
144  else {
145  // above 1650 MeV - angular distribution (x=cos(theta): (ax^2+bx+c)*(0.5+(arctan(10*(x+dev)))/pi) + vert
146 
147  G4double a2=-0.29;
148  G4double b2=0.348; // ax^2+bx+c: around cos(theta)=0.6 with maximum at 0.644963 (value = 0.1872666)
149  G4double c2=0.0546;
150  G4double dev=-0.2; // tail close to zero from "dev" down to -1
151  G4double vert=0.04; // to avoid negative differential cross sections
152 
153  G4double interg2=0.1716182902205207; // with the above given parameters! (integral to normalize)
154  const G4double f2=1.09118088; // maximum (integral taken into account)
155 
156  G4int passe2=0;
157  while (passe2==0) {
158  // Sample x from -1 to 1
159  x1=Random::shoot();
160  if (Random::shoot() > 0.5) x1=-x1;
161 
162  // Sample u from 0 to 1
163  u1=Random::shoot();
164  fteta=((a2*x1*x1+b2*x1+c2)*(0.5+(std::atan(10*(x1+dev)))/pi) + vert)/interg2;
165  // The condition
166  if (u1*f2 < fteta) {
167  teta=std::acos(x1);
168  passe2=1;
169  }
170  }
171  }
172 
173  fi=(2.0*pi)*Random::shoot();
174 
175  ThreeVector mom_nucleon(
176  pn*std::sin(teta)*std::cos(fi),
177  pn*std::sin(teta)*std::sin(fi),
178  pn*std::cos(teta)
179  );
180 // end real distribution
181 
182  nucleon->setMomentum(-mom_nucleon);
183  eta->setMomentum(mom_nucleon);
184 
185  fs->addModifiedParticle(nucleon);
186  fs->addModifiedParticle(eta);
187  }
G4int
int G4int
Definition: G4Types.hh:78
G4InuclParticleNames::nucleon
G4bool nucleon(G4int ityp)
Definition: G4InuclParticleNames.hh:95
G4INCL::Particle::isNucleon
G4bool isNucleon() const
Definition: G4INCLParticle.hh:232
G4INCL::Random::shoot
G4double shoot()
Definition: G4INCLRandom.cc:93
pi
static constexpr double pi
Definition: G4SIunits.hh:75
G4double
double G4double
Definition: G4Types.hh:76
G4INCL::KinematicsUtils::totalEnergyInCM
G4double totalEnergyInCM(Particle const *const p1, Particle const *const p2)
Definition: G4INCLKinematicsUtils.cc:93

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The documentation for this class was generated from the following files: