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25 // 25 //
26 // G4MuonDecayChannelWithSpin class implementa << 26 // ------------------------------------------------------------
>> 27 // GEANT 4 class header file
>> 28 //
>> 29 // History:
>> 30 // 17 August 2004 P.Gumplinger and T.MacPhail
>> 31 // samples Michel spectrum including 1st order
>> 32 // radiative corrections
>> 33 // Reference: Florian Scheck "Muon Physics", in Physics Reports
>> 34 // (Review Section of Physics Letters) 44, No. 4 (1978)
>> 35 // 187-248. North-Holland Publishing Company, Amsterdam
>> 36 // at page 210 cc.
>> 37 //
>> 38 // W.E. Fisher and F. Scheck, Nucl. Phys. B83 (1974) 25.
>> 39 //
>> 40 // ------------------------------------------------------------
27 // 41 //
28 // References: <<
29 // - Florian Scheck "Muon Physics", in Physics <<
30 // (Review Section of Physics Letters) 44, N <<
31 // 187-248. North-Holland Publishing Company <<
32 // - W.E. Fisher and F. Scheck, Nucl. Phys. B8 <<
33 <<
34 // Authors: P.Gumplinger and T.MacPhail, 17 Au <<
35 // ------------------------------------------- <<
36 <<
37 #include "G4MuonDecayChannelWithSpin.hh" 42 #include "G4MuonDecayChannelWithSpin.hh"
38 43
>> 44 #include "Randomize.hh"
39 #include "G4DecayProducts.hh" 45 #include "G4DecayProducts.hh"
40 #include "G4LorentzVector.hh" 46 #include "G4LorentzVector.hh"
41 #include "G4PhysicalConstants.hh" <<
42 #include "G4SystemOfUnits.hh" <<
43 #include "Randomize.hh" <<
44 47
45 G4MuonDecayChannelWithSpin::G4MuonDecayChannel << 48 G4MuonDecayChannelWithSpin::G4MuonDecayChannelWithSpin(const G4String& theParentName,
46 << 49 G4double theBR)
47 : G4MuonDecayChannel(theParentName, theBR) << 50 : G4MuonDecayChannel(theParentName,theBR)
48 {} << 51 {
>> 52 }
49 53
50 G4MuonDecayChannelWithSpin& << 54 G4MuonDecayChannelWithSpin::~G4MuonDecayChannelWithSpin()
51 G4MuonDecayChannelWithSpin::operator=(const G4 <<
52 { 55 {
53 if (this != &right) { <<
54 kinematics_name = right.kinematics_name; <<
55 verboseLevel = right.verboseLevel; <<
56 rbranch = right.rbranch; <<
57 <<
58 // copy parent name <<
59 delete parent_name; <<
60 parent_name = new G4String(*right.parent_n <<
61 <<
62 // clear daughters_name array <<
63 ClearDaughtersName(); <<
64 <<
65 // recreate array <<
66 numberOfDaughters = right.numberOfDaughter <<
67 if (numberOfDaughters > 0) { <<
68 daughters_name = new G4String*[numberOfD <<
69 // copy daughters name <<
70 for (G4int index = 0; index < numberOfDa <<
71 daughters_name[index] = new G4String(* <<
72 } <<
73 } <<
74 } <<
75 return *this; <<
76 } 56 }
77 57
78 G4DecayProducts* G4MuonDecayChannelWithSpin::D << 58 G4DecayProducts *G4MuonDecayChannelWithSpin::DecayIt(G4double)
79 { 59 {
80 // This version assumes V-A coupling with 1s 60 // This version assumes V-A coupling with 1st order radiative correctons,
81 // the standard model Michel pa 61 // the standard model Michel parameter values, but
82 // gives incorrect energy spect 62 // gives incorrect energy spectrum for neutrinos
83 63
84 #ifdef G4VERBOSE 64 #ifdef G4VERBOSE
85 if (GetVerboseLevel() > 1) G4cout << "G4Muon << 65 if (GetVerboseLevel()>1) G4cout << "G4MuonDecayChannelWithSpin::DecayIt ";
86 #endif 66 #endif
87 67
88 CheckAndFillParent(); << 68 if (parent == 0) FillParent();
89 CheckAndFillDaughters(); << 69 if (daughters == 0) FillDaughters();
90 70
91 // parent mass 71 // parent mass
92 G4double parentmass = G4MT_parent->GetPDGMas << 72 G4double parentmass = parent->GetPDGMass();
93 73
94 G4double EMMU = parentmass; << 74 EMMU = parentmass;
95 75
96 // daughters'mass << 76 //daughters'mass
97 G4double daughtermass[3]; << 77 G4double daughtermass[3];
98 // G4double sumofdaughtermass = 0.0; << 78 G4double sumofdaughtermass = 0.0;
99 for (G4int index = 0; index < 3; ++index) { << 79 for (G4int index=0; index<3; index++){
100 daughtermass[index] = G4MT_daughters[index << 80 daughtermass[index] = daughters[index]->GetPDGMass();
101 // sumofdaughtermass += daughtermass[index << 81 sumofdaughtermass += daughtermass[index];
102 } 82 }
103 83
104 G4double EMASS = daughtermass[0]; << 84 EMASS = daughtermass[0];
105 85
106 // create parent G4DynamicParticle at rest << 86 //create parent G4DynamicParticle at rest
107 G4ThreeVector dummy; 87 G4ThreeVector dummy;
108 auto parentparticle = new G4DynamicParticle( << 88 G4DynamicParticle * parentparticle = new G4DynamicParticle( parent, dummy, 0.0);
109 // create G4Decayproducts << 89 //create G4Decayproducts
110 auto products = new G4DecayProducts(*parentp << 90 G4DecayProducts *products = new G4DecayProducts(*parentparticle);
111 delete parentparticle; 91 delete parentparticle;
112 92
113 // calculate electron energy << 93 // calcurate electron energy
114 94
115 G4double michel_rho = 0.75; // Standard Mod << 95 G4double michel_rho = 0.75; //Standard Model Michel rho
116 G4double michel_delta = 0.75; // Standard M << 96 G4double michel_delta = 0.75; //Standard Model Michel delta
117 G4double michel_xsi = 1.00; // Standard Mod << 97 G4double michel_xsi = 1.00; //Standard Model Michel xsi
118 G4double michel_eta = 0.00; // Standard Mod << 98 G4double michel_eta = 0.00; //Standard Model eta
119 99
120 G4double rndm, x, ctheta; 100 G4double rndm, x, ctheta;
121 101
122 G4double FG; << 102 G4double FG;
123 G4double FG_max = 2.00; 103 G4double FG_max = 2.00;
124 104
125 G4double W_mue = (EMMU * EMMU + EMASS * EMAS << 105 G4double W_mue = (EMMU*EMMU+EMASS*EMASS)/(2.*EMMU);
126 G4double x0 = EMASS / W_mue; << 106 G4double x0 = EMASS/W_mue;
127 107
128 G4double x0_squared = x0 * x0; << 108 G4double x0_squared = x0*x0;
129 109
130 // ***************************************** 110 // ***************************************************
131 // x0 <= x <= 1. and -1 <= y <= 1 111 // x0 <= x <= 1. and -1 <= y <= 1
132 // 112 //
133 // F(x,y) = f(x)*g(x,y); g(x,y) = 1.+g 113 // F(x,y) = f(x)*g(x,y); g(x,y) = 1.+g(x)*y
134 // ***************************************** 114 // ***************************************************
135 115
136 // ***** sampling F(x,y) directly (brute for 116 // ***** sampling F(x,y) directly (brute force) *****
137 117
138 const std::size_t MAX_LOOP = 10000; << 118 do{
139 for (std::size_t loop_count = 0; loop_count << 119
140 // Sample the positron energy by sampling 120 // Sample the positron energy by sampling from F
141 121
142 rndm = G4UniformRand(); 122 rndm = G4UniformRand();
143 123
144 x = x0 + rndm * (1. - x0); << 124 x = x0 + rndm*(1.-x0);
145 125
146 G4double x_squared = x * x; << 126 G4double x_squared = x*x;
147 127
148 G4double F_IS, F_AS, G_IS, G_AS; 128 G4double F_IS, F_AS, G_IS, G_AS;
149 129
150 F_IS = 1. / 6. * (-2. * x_squared + 3. * x << 130 F_IS = 1./6.*(-2.*x_squared+3.*x-x0_squared);
151 F_AS = 1. / 6. * std::sqrt(x_squared - x0_ << 131 F_AS = 1./6.*std::sqrt(x_squared-x0_squared)*(2.*x-2.+std::sqrt(1.-x0_squared));
152 132
153 G_IS = 2. / 9. * (michel_rho - 0.75) * (4. << 133 G_IS = 2./9.*(michel_rho-0.75)*(4.*x_squared-3.*x-x0_squared);
154 G_IS = G_IS + michel_eta * (1. - x) * x0; << 134 G_IS = G_IS + michel_eta*(1.-x)*x0;
155 135
156 G_AS = 3. * (michel_xsi - 1.) * (1. - x); << 136 G_AS = 3.*(michel_xsi-1.)*(1.-x);
157 G_AS = << 137 G_AS = G_AS+2.*(michel_xsi*michel_delta-0.75)*(4.*x-4.+std::sqrt(1.-x0_squared));
158 G_AS + 2. * (michel_xsi * michel_delta - << 138 G_AS = 1./9.*std::sqrt(x_squared-x0_squared)*G_AS;
159 G_AS = 1. / 9. * std::sqrt(x_squared - x0_ <<
160 139
161 F_IS = F_IS + G_IS; 140 F_IS = F_IS + G_IS;
162 F_AS = F_AS + G_AS; 141 F_AS = F_AS + G_AS;
163 142
164 // *** Radiative Corrections *** 143 // *** Radiative Corrections ***
165 144
166 const G4double omega = std::log(EMMU / EMA << 145 G4double R_IS = F_c(x,x0);
167 G4double R_IS = F_c(x, x0, omega); <<
168 146
169 G4double F = 6. * F_IS + R_IS / std::sqrt( << 147 G4double F = 6.*F_IS + R_IS/std::sqrt(x_squared-x0_squared);
170 148
171 // *** Radiative Corrections *** 149 // *** Radiative Corrections ***
172 150
173 G4double R_AS = F_theta(x, x0, omega); << 151 G4double R_AS = F_theta(x,x0);
174 152
175 rndm = G4UniformRand(); 153 rndm = G4UniformRand();
176 154
177 ctheta = 2. * rndm - 1.; << 155 ctheta = 2.*rndm-1.;
178 156
179 G4double G = 6. * F_AS - R_AS / std::sqrt( << 157 G4double G = 6.*F_AS - R_AS/std::sqrt(x_squared-x0_squared);
180 158
181 FG = std::sqrt(x_squared - x0_squared) * F << 159 FG = std::sqrt(x_squared-x0_squared)*F*(1.+(G/F)*ctheta);
182 160
183 if (FG > FG_max) { << 161 if(FG>FG_max){
184 G4Exception("G4MuonDecayChannelWithSpin: << 162 G4cout<<"***Problem in Muon Decay *** : FG > FG_max"<<G4endl;
185 "Problem in Muon Decay: FG > <<
186 FG_max = FG; 163 FG_max = FG;
187 } 164 }
188 165
189 rndm = G4UniformRand(); 166 rndm = G4UniformRand();
190 167
191 if (FG >= rndm * FG_max) break; << 168 }while(FG<rndm*FG_max);
192 } <<
193 169
194 G4double energy = x * W_mue; 170 G4double energy = x * W_mue;
195 171
196 rndm = G4UniformRand(); 172 rndm = G4UniformRand();
197 173
198 G4double phi = twopi * rndm; 174 G4double phi = twopi * rndm;
199 175
200 if (energy < EMASS) energy = EMASS; << 176 if(energy < EMASS) energy = EMASS;
201 177
202 // Calculate daughter momentum << 178 // calculate daughter momentum
203 G4double daughtermomentum[3]; 179 G4double daughtermomentum[3];
204 180
205 daughtermomentum[0] = std::sqrt(energy * ene << 181 daughtermomentum[0] = std::sqrt(energy*energy - EMASS*EMASS);
206 182
207 G4double stheta = std::sqrt(1. - ctheta * ct << 183 G4double stheta = std::sqrt(1.-ctheta*ctheta);
208 G4double cphi = std::cos(phi); 184 G4double cphi = std::cos(phi);
209 G4double sphi = std::sin(phi); 185 G4double sphi = std::sin(phi);
210 186
211 // Coordinates of the decay positron with re << 187 //Coordinates of the decay positron with respect to the muon spin
212 G4double px = stheta * cphi; << 188
213 G4double py = stheta * sphi; << 189 G4double px = stheta*cphi;
>> 190 G4double py = stheta*sphi;
214 G4double pz = ctheta; 191 G4double pz = ctheta;
215 192
216 G4ThreeVector direction0(px, py, pz); << 193 G4ThreeVector direction0(px,py,pz);
217 194
218 direction0.rotateUz(parent_polarization); 195 direction0.rotateUz(parent_polarization);
219 196
220 auto daughterparticle0 = << 197 G4DynamicParticle * daughterparticle0
221 new G4DynamicParticle(G4MT_daughters[0], d << 198 = new G4DynamicParticle( daughters[0], daughtermomentum[0]*direction0);
222 199
223 products->PushProducts(daughterparticle0); 200 products->PushProducts(daughterparticle0);
224 201
>> 202
225 // daughter 1 ,2 (neutrinos) 203 // daughter 1 ,2 (neutrinos)
226 // create neutrinos in the C.M frame of two 204 // create neutrinos in the C.M frame of two neutrinos
227 G4double energy2 = parentmass - energy; << 205 G4double energy2 = parentmass*(1.0 - x/2.0);
228 G4double vmass = std::sqrt((energy2 - daught << 206 G4double vmass = std::sqrt((energy2-daughtermomentum[0])*(energy2+daughtermomentum[0]));
229 G4double beta = -1.0 * daughtermomentum[0] / << 207 G4double beta = -1.0*daughtermomentum[0]/energy2;
230 G4double costhetan = 2. * G4UniformRand() - << 208 G4double costhetan = 2.*G4UniformRand()-1.0;
231 G4double sinthetan = std::sqrt((1.0 - costhe << 209 G4double sinthetan = std::sqrt((1.0-costhetan)*(1.0+costhetan));
232 G4double phin = twopi * G4UniformRand() * ra << 210 G4double phin = twopi*G4UniformRand()*rad;
233 G4double sinphin = std::sin(phin); 211 G4double sinphin = std::sin(phin);
234 G4double cosphin = std::cos(phin); 212 G4double cosphin = std::cos(phin);
235 213
236 G4ThreeVector direction1(sinthetan * cosphin << 214 G4ThreeVector direction1(sinthetan*cosphin,sinthetan*sinphin,costhetan);
237 auto daughterparticle1 = new G4DynamicPartic << 215 G4DynamicParticle * daughterparticle1
238 auto daughterparticle2 = << 216 = new G4DynamicParticle( daughters[1], direction1*(vmass/2.));
239 new G4DynamicParticle(G4MT_daughters[2], d << 217 G4DynamicParticle * daughterparticle2
>> 218 = new G4DynamicParticle( daughters[2], direction1*(-1.0*vmass/2.));
240 219
241 // boost to the muon rest frame 220 // boost to the muon rest frame
242 G4LorentzVector p4; 221 G4LorentzVector p4;
243 p4 = daughterparticle1->Get4Momentum(); 222 p4 = daughterparticle1->Get4Momentum();
244 p4.boost(direction0.x() * beta, direction0.y << 223 p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
245 daughterparticle1->Set4Momentum(p4); 224 daughterparticle1->Set4Momentum(p4);
246 p4 = daughterparticle2->Get4Momentum(); 225 p4 = daughterparticle2->Get4Momentum();
247 p4.boost(direction0.x() * beta, direction0.y << 226 p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
248 daughterparticle2->Set4Momentum(p4); 227 daughterparticle2->Set4Momentum(p4);
249 products->PushProducts(daughterparticle1); 228 products->PushProducts(daughterparticle1);
250 products->PushProducts(daughterparticle2); 229 products->PushProducts(daughterparticle2);
251 daughtermomentum[1] = daughterparticle1->Get 230 daughtermomentum[1] = daughterparticle1->GetTotalMomentum();
252 daughtermomentum[2] = daughterparticle2->Get 231 daughtermomentum[2] = daughterparticle2->GetTotalMomentum();
253 232
254 // output message 233 // output message
255 #ifdef G4VERBOSE 234 #ifdef G4VERBOSE
256 if (GetVerboseLevel() > 1) { << 235 if (GetVerboseLevel()>1) {
257 G4cout << "G4MuonDecayChannelWithSpin::Dec 236 G4cout << "G4MuonDecayChannelWithSpin::DecayIt ";
258 G4cout << " create decay products in rest << 237 G4cout << " create decay products in rest frame " <<G4endl;
259 G4double TT = daughterparticle0->GetTotalE << 238 products->DumpInfo();
260 + daughterparticle2->GetTota <<
261 G4cout << "e " << daughterparticle0->GetT <<
262 G4cout << "nu1" << daughterparticle1->GetT <<
263 G4cout << "nu2" << daughterparticle2->GetT <<
264 G4cout << "total" << (TT - parentmass) / k <<
265 if (GetVerboseLevel() > 2) { <<
266 products->DumpInfo(); <<
267 } <<
268 } 239 }
269 #endif 240 #endif
270 <<
271 return products; 241 return products;
272 } 242 }
273 243
274 G4double G4MuonDecayChannelWithSpin::R_c(G4dou << 244 G4double G4MuonDecayChannelWithSpin::R_c(G4double x){
275 { <<
276 auto n_max = (G4int)(100. * x); <<
277 245
278 if (n_max < 10) n_max = 10; << 246 G4int n_max = (int)(100.*x);
>> 247
>> 248 if(n_max<10)n_max=10;
279 249
280 G4double L2 = 0.0; 250 G4double L2 = 0.0;
281 251
282 for (G4int n = 1; n <= n_max; ++n) { << 252 for(G4int n=1; n<=n_max; n++){
283 L2 += std::pow(x, n) / (n * n); << 253 L2 += std::pow(x,n)/(n*n);
284 } 254 }
285 255
>> 256 G4double omega = std::log(EMMU/EMASS);
>> 257
286 G4double r_c; 258 G4double r_c;
287 259
288 r_c = 2. * L2 - (pi * pi / 3.) - 2.; << 260 r_c = 2.*L2-(pi*pi/3.)-2.;
289 r_c = r_c + omega * (1.5 + 2. * std::log((1. << 261 r_c = r_c + omega * (1.5+2.*std::log((1.-x)/x));
290 r_c = r_c - std::log(x) * (2. * std::log(x) << 262 r_c = r_c - std::log(x)*(2.*std::log(x)-1.);
291 r_c = r_c + (3. * std::log(x) - 1. - 1. / x) << 263 r_c = r_c + (3.*std::log(x)-1.-1./x)*std::log(1.-x);
292 264
293 return r_c; 265 return r_c;
294 } 266 }
295 267