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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
39 #include "G4DecayProducts.hh" <<
40 #include "G4LorentzVector.hh" <<
41 #include "G4PhysicalConstants.hh" 44 #include "G4PhysicalConstants.hh"
42 #include "G4SystemOfUnits.hh" 45 #include "G4SystemOfUnits.hh"
43 #include "Randomize.hh" 46 #include "Randomize.hh"
44 47
45 G4MuonDecayChannelWithSpin::G4MuonDecayChannel << 48 #include "G4DecayProducts.hh"
46 << 49 #include "G4LorentzVector.hh"
47 : G4MuonDecayChannel(theParentName, theBR) << 50
48 {} << 51 G4MuonDecayChannelWithSpin::G4MuonDecayChannelWithSpin()
>> 52 : G4MuonDecayChannel(),
>> 53 parent_polarization(),
>> 54 EMMU( 0.*MeV),
>> 55 EMASS( 0.*MeV)
>> 56 {
>> 57 }
>> 58
>> 59 G4MuonDecayChannelWithSpin::G4MuonDecayChannelWithSpin(const G4String& theParentName,
>> 60 G4double theBR)
>> 61 : G4MuonDecayChannel(theParentName,theBR),
>> 62 parent_polarization(),
>> 63 EMMU( 0.*MeV),
>> 64 EMASS( 0.*MeV)
>> 65 {
>> 66 }
49 67
50 G4MuonDecayChannelWithSpin& << 68 G4MuonDecayChannelWithSpin::~G4MuonDecayChannelWithSpin()
51 G4MuonDecayChannelWithSpin::operator=(const G4 <<
52 { 69 {
53 if (this != &right) { << 70 }
>> 71
>> 72 G4MuonDecayChannelWithSpin::G4MuonDecayChannelWithSpin(const G4MuonDecayChannelWithSpin &right):
>> 73 G4MuonDecayChannel(right)
>> 74 {
>> 75 parent_polarization = right.parent_polarization;
>> 76 EMMU = right.EMMU;
>> 77 EMASS = right.EMASS;
>> 78 }
>> 79
>> 80 G4MuonDecayChannelWithSpin & G4MuonDecayChannelWithSpin::operator=(const G4MuonDecayChannelWithSpin & right)
>> 81 {
>> 82 if (this != &right) {
54 kinematics_name = right.kinematics_name; 83 kinematics_name = right.kinematics_name;
55 verboseLevel = right.verboseLevel; 84 verboseLevel = right.verboseLevel;
56 rbranch = right.rbranch; 85 rbranch = right.rbranch;
57 86
58 // copy parent name 87 // copy parent name
59 delete parent_name; <<
60 parent_name = new G4String(*right.parent_n 88 parent_name = new G4String(*right.parent_name);
61 89
62 // clear daughters_name array 90 // clear daughters_name array
63 ClearDaughtersName(); 91 ClearDaughtersName();
64 92
65 // recreate array 93 // recreate array
66 numberOfDaughters = right.numberOfDaughter 94 numberOfDaughters = right.numberOfDaughters;
67 if (numberOfDaughters > 0) { << 95 if ( numberOfDaughters >0 ) {
>> 96 if (daughters_name !=0) ClearDaughtersName();
68 daughters_name = new G4String*[numberOfD 97 daughters_name = new G4String*[numberOfDaughters];
69 // copy daughters name << 98 //copy daughters name
70 for (G4int index = 0; index < numberOfDa << 99 for (G4int index=0; index < numberOfDaughters; index++) {
71 daughters_name[index] = new G4String(* << 100 daughters_name[index] = new G4String(*right.daughters_name[index]);
72 } 101 }
73 } 102 }
>> 103 parent_polarization = right.parent_polarization;
>> 104 EMMU = right.EMMU;
>> 105 EMASS = right.EMASS;
74 } 106 }
75 return *this; 107 return *this;
76 } 108 }
77 109
78 G4DecayProducts* G4MuonDecayChannelWithSpin::D << 110
>> 111 G4DecayProducts *G4MuonDecayChannelWithSpin::DecayIt(G4double)
79 { 112 {
80 // This version assumes V-A coupling with 1s 113 // This version assumes V-A coupling with 1st order radiative correctons,
81 // the standard model Michel pa 114 // the standard model Michel parameter values, but
82 // gives incorrect energy spect 115 // gives incorrect energy spectrum for neutrinos
83 116
84 #ifdef G4VERBOSE 117 #ifdef G4VERBOSE
85 if (GetVerboseLevel() > 1) G4cout << "G4Muon << 118 if (GetVerboseLevel()>1) G4cout << "G4MuonDecayChannelWithSpin::DecayIt ";
86 #endif 119 #endif
87 120
88 CheckAndFillParent(); << 121 if (G4MT_parent == 0) FillParent();
89 CheckAndFillDaughters(); << 122 if (G4MT_daughters == 0) FillDaughters();
90 123
91 // parent mass 124 // parent mass
92 G4double parentmass = G4MT_parent->GetPDGMas 125 G4double parentmass = G4MT_parent->GetPDGMass();
93 126
94 G4double EMMU = parentmass; << 127 EMMU = parentmass;
95 128
96 // daughters'mass << 129 //daughters'mass
97 G4double daughtermass[3]; << 130 G4double daughtermass[3];
98 // G4double sumofdaughtermass = 0.0; << 131 G4double sumofdaughtermass = 0.0;
99 for (G4int index = 0; index < 3; ++index) { << 132 for (G4int index=0; index<3; index++){
100 daughtermass[index] = G4MT_daughters[index 133 daughtermass[index] = G4MT_daughters[index]->GetPDGMass();
101 // sumofdaughtermass += daughtermass[index << 134 sumofdaughtermass += daughtermass[index];
102 } 135 }
103 136
104 G4double EMASS = daughtermass[0]; << 137 EMASS = daughtermass[0];
105 138
106 // create parent G4DynamicParticle at rest << 139 //create parent G4DynamicParticle at rest
107 G4ThreeVector dummy; 140 G4ThreeVector dummy;
108 auto parentparticle = new G4DynamicParticle( << 141 G4DynamicParticle * parentparticle = new G4DynamicParticle( G4MT_parent, dummy, 0.0);
109 // create G4Decayproducts << 142 //create G4Decayproducts
110 auto products = new G4DecayProducts(*parentp << 143 G4DecayProducts *products = new G4DecayProducts(*parentparticle);
111 delete parentparticle; 144 delete parentparticle;
112 145
113 // calculate electron energy << 146 // calcurate electron energy
114 147
115 G4double michel_rho = 0.75; // Standard Mod << 148 G4double michel_rho = 0.75; //Standard Model Michel rho
116 G4double michel_delta = 0.75; // Standard M << 149 G4double michel_delta = 0.75; //Standard Model Michel delta
117 G4double michel_xsi = 1.00; // Standard Mod << 150 G4double michel_xsi = 1.00; //Standard Model Michel xsi
118 G4double michel_eta = 0.00; // Standard Mod << 151 G4double michel_eta = 0.00; //Standard Model eta
119 152
120 G4double rndm, x, ctheta; 153 G4double rndm, x, ctheta;
121 154
122 G4double FG; << 155 G4double FG;
123 G4double FG_max = 2.00; 156 G4double FG_max = 2.00;
124 157
125 G4double W_mue = (EMMU * EMMU + EMASS * EMAS << 158 G4double W_mue = (EMMU*EMMU+EMASS*EMASS)/(2.*EMMU);
126 G4double x0 = EMASS / W_mue; << 159 G4double x0 = EMASS/W_mue;
127 160
128 G4double x0_squared = x0 * x0; << 161 G4double x0_squared = x0*x0;
129 162
130 // ***************************************** 163 // ***************************************************
131 // x0 <= x <= 1. and -1 <= y <= 1 164 // x0 <= x <= 1. and -1 <= y <= 1
132 // 165 //
133 // F(x,y) = f(x)*g(x,y); g(x,y) = 1.+g 166 // F(x,y) = f(x)*g(x,y); g(x,y) = 1.+g(x)*y
134 // ***************************************** 167 // ***************************************************
135 168
136 // ***** sampling F(x,y) directly (brute for 169 // ***** sampling F(x,y) directly (brute force) *****
137 170
138 const std::size_t MAX_LOOP = 10000; << 171 do{
139 for (std::size_t loop_count = 0; loop_count << 172
140 // Sample the positron energy by sampling 173 // Sample the positron energy by sampling from F
141 174
142 rndm = G4UniformRand(); 175 rndm = G4UniformRand();
143 176
144 x = x0 + rndm * (1. - x0); << 177 x = x0 + rndm*(1.-x0);
145 178
146 G4double x_squared = x * x; << 179 G4double x_squared = x*x;
147 180
148 G4double F_IS, F_AS, G_IS, G_AS; 181 G4double F_IS, F_AS, G_IS, G_AS;
149 182
150 F_IS = 1. / 6. * (-2. * x_squared + 3. * x << 183 F_IS = 1./6.*(-2.*x_squared+3.*x-x0_squared);
151 F_AS = 1. / 6. * std::sqrt(x_squared - x0_ << 184 F_AS = 1./6.*std::sqrt(x_squared-x0_squared)*(2.*x-2.+std::sqrt(1.-x0_squared));
152 185
153 G_IS = 2. / 9. * (michel_rho - 0.75) * (4. << 186 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; << 187 G_IS = G_IS + michel_eta*(1.-x)*x0;
155 188
156 G_AS = 3. * (michel_xsi - 1.) * (1. - x); << 189 G_AS = 3.*(michel_xsi-1.)*(1.-x);
157 G_AS = << 190 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 - << 191 G_AS = 1./9.*std::sqrt(x_squared-x0_squared)*G_AS;
159 G_AS = 1. / 9. * std::sqrt(x_squared - x0_ <<
160 192
161 F_IS = F_IS + G_IS; 193 F_IS = F_IS + G_IS;
162 F_AS = F_AS + G_AS; 194 F_AS = F_AS + G_AS;
163 195
164 // *** Radiative Corrections *** 196 // *** Radiative Corrections ***
165 197
166 const G4double omega = std::log(EMMU / EMA << 198 G4double R_IS = F_c(x,x0);
167 G4double R_IS = F_c(x, x0, omega); <<
168 199
169 G4double F = 6. * F_IS + R_IS / std::sqrt( << 200 G4double F = 6.*F_IS + R_IS/std::sqrt(x_squared-x0_squared);
170 201
171 // *** Radiative Corrections *** 202 // *** Radiative Corrections ***
172 203
173 G4double R_AS = F_theta(x, x0, omega); << 204 G4double R_AS = F_theta(x,x0);
174 205
175 rndm = G4UniformRand(); 206 rndm = G4UniformRand();
176 207
177 ctheta = 2. * rndm - 1.; << 208 ctheta = 2.*rndm-1.;
178 209
179 G4double G = 6. * F_AS - R_AS / std::sqrt( << 210 G4double G = 6.*F_AS - R_AS/std::sqrt(x_squared-x0_squared);
180 211
181 FG = std::sqrt(x_squared - x0_squared) * F << 212 FG = std::sqrt(x_squared-x0_squared)*F*(1.+(G/F)*ctheta);
182 213
183 if (FG > FG_max) { << 214 if(FG>FG_max){
184 G4Exception("G4MuonDecayChannelWithSpin: << 215 G4cout<<"***Problem in Muon Decay *** : FG > FG_max"<<G4endl;
185 "Problem in Muon Decay: FG > <<
186 FG_max = FG; 216 FG_max = FG;
187 } 217 }
188 218
189 rndm = G4UniformRand(); 219 rndm = G4UniformRand();
190 220
191 if (FG >= rndm * FG_max) break; << 221 }while(FG<rndm*FG_max);
192 } <<
193 222
194 G4double energy = x * W_mue; 223 G4double energy = x * W_mue;
195 224
196 rndm = G4UniformRand(); 225 rndm = G4UniformRand();
197 226
198 G4double phi = twopi * rndm; 227 G4double phi = twopi * rndm;
199 228
200 if (energy < EMASS) energy = EMASS; << 229 if(energy < EMASS) energy = EMASS;
201 230
202 // Calculate daughter momentum << 231 // calculate daughter momentum
203 G4double daughtermomentum[3]; 232 G4double daughtermomentum[3];
204 233
205 daughtermomentum[0] = std::sqrt(energy * ene << 234 daughtermomentum[0] = std::sqrt(energy*energy - EMASS*EMASS);
206 235
207 G4double stheta = std::sqrt(1. - ctheta * ct << 236 G4double stheta = std::sqrt(1.-ctheta*ctheta);
208 G4double cphi = std::cos(phi); 237 G4double cphi = std::cos(phi);
209 G4double sphi = std::sin(phi); 238 G4double sphi = std::sin(phi);
210 239
211 // Coordinates of the decay positron with re << 240 //Coordinates of the decay positron with respect to the muon spin
212 G4double px = stheta * cphi; << 241
213 G4double py = stheta * sphi; << 242 G4double px = stheta*cphi;
>> 243 G4double py = stheta*sphi;
214 G4double pz = ctheta; 244 G4double pz = ctheta;
215 245
216 G4ThreeVector direction0(px, py, pz); << 246 G4ThreeVector direction0(px,py,pz);
217 247
218 direction0.rotateUz(parent_polarization); 248 direction0.rotateUz(parent_polarization);
219 249
220 auto daughterparticle0 = << 250 G4DynamicParticle * daughterparticle0
221 new G4DynamicParticle(G4MT_daughters[0], d << 251 = new G4DynamicParticle( G4MT_daughters[0], daughtermomentum[0]*direction0);
222 252
223 products->PushProducts(daughterparticle0); 253 products->PushProducts(daughterparticle0);
224 254
>> 255
225 // daughter 1 ,2 (neutrinos) 256 // daughter 1 ,2 (neutrinos)
226 // create neutrinos in the C.M frame of two 257 // create neutrinos in the C.M frame of two neutrinos
227 G4double energy2 = parentmass - energy; << 258 G4double energy2 = parentmass*(1.0 - x/2.0);
228 G4double vmass = std::sqrt((energy2 - daught << 259 G4double vmass = std::sqrt((energy2-daughtermomentum[0])*(energy2+daughtermomentum[0]));
229 G4double beta = -1.0 * daughtermomentum[0] / << 260 G4double beta = -1.0*daughtermomentum[0]/energy2;
230 G4double costhetan = 2. * G4UniformRand() - << 261 G4double costhetan = 2.*G4UniformRand()-1.0;
231 G4double sinthetan = std::sqrt((1.0 - costhe << 262 G4double sinthetan = std::sqrt((1.0-costhetan)*(1.0+costhetan));
232 G4double phin = twopi * G4UniformRand() * ra << 263 G4double phin = twopi*G4UniformRand()*rad;
233 G4double sinphin = std::sin(phin); 264 G4double sinphin = std::sin(phin);
234 G4double cosphin = std::cos(phin); 265 G4double cosphin = std::cos(phin);
235 266
236 G4ThreeVector direction1(sinthetan * cosphin << 267 G4ThreeVector direction1(sinthetan*cosphin,sinthetan*sinphin,costhetan);
237 auto daughterparticle1 = new G4DynamicPartic << 268 G4DynamicParticle * daughterparticle1
238 auto daughterparticle2 = << 269 = new G4DynamicParticle( G4MT_daughters[1], direction1*(vmass/2.));
239 new G4DynamicParticle(G4MT_daughters[2], d << 270 G4DynamicParticle * daughterparticle2
>> 271 = new G4DynamicParticle( G4MT_daughters[2], direction1*(-1.0*vmass/2.));
240 272
241 // boost to the muon rest frame 273 // boost to the muon rest frame
242 G4LorentzVector p4; 274 G4LorentzVector p4;
243 p4 = daughterparticle1->Get4Momentum(); 275 p4 = daughterparticle1->Get4Momentum();
244 p4.boost(direction0.x() * beta, direction0.y << 276 p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
245 daughterparticle1->Set4Momentum(p4); 277 daughterparticle1->Set4Momentum(p4);
246 p4 = daughterparticle2->Get4Momentum(); 278 p4 = daughterparticle2->Get4Momentum();
247 p4.boost(direction0.x() * beta, direction0.y << 279 p4.boost( direction0.x()*beta, direction0.y()*beta, direction0.z()*beta);
248 daughterparticle2->Set4Momentum(p4); 280 daughterparticle2->Set4Momentum(p4);
249 products->PushProducts(daughterparticle1); 281 products->PushProducts(daughterparticle1);
250 products->PushProducts(daughterparticle2); 282 products->PushProducts(daughterparticle2);
251 daughtermomentum[1] = daughterparticle1->Get 283 daughtermomentum[1] = daughterparticle1->GetTotalMomentum();
252 daughtermomentum[2] = daughterparticle2->Get 284 daughtermomentum[2] = daughterparticle2->GetTotalMomentum();
253 285
254 // output message 286 // output message
255 #ifdef G4VERBOSE 287 #ifdef G4VERBOSE
256 if (GetVerboseLevel() > 1) { << 288 if (GetVerboseLevel()>1) {
257 G4cout << "G4MuonDecayChannelWithSpin::Dec 289 G4cout << "G4MuonDecayChannelWithSpin::DecayIt ";
258 G4cout << " create decay products in rest << 290 G4cout << " create decay products in rest frame " <<G4endl;
259 G4double TT = daughterparticle0->GetTotalE << 291 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 } 292 }
269 #endif 293 #endif
270 <<
271 return products; 294 return products;
272 } 295 }
273 296
274 G4double G4MuonDecayChannelWithSpin::R_c(G4dou << 297 G4double G4MuonDecayChannelWithSpin::R_c(G4double x){
275 { << 298
276 auto n_max = (G4int)(100. * x); << 299 G4int n_max = (int)(100.*x);
277 300
278 if (n_max < 10) n_max = 10; << 301 if(n_max<10)n_max=10;
279 302
280 G4double L2 = 0.0; 303 G4double L2 = 0.0;
281 304
282 for (G4int n = 1; n <= n_max; ++n) { << 305 for(G4int n=1; n<=n_max; n++){
283 L2 += std::pow(x, n) / (n * n); << 306 L2 += std::pow(x,n)/(n*n);
284 } 307 }
285 308
>> 309 G4double omega = std::log(EMMU/EMASS);
>> 310
286 G4double r_c; 311 G4double r_c;
287 312
288 r_c = 2. * L2 - (pi * pi / 3.) - 2.; << 313 r_c = 2.*L2-(pi*pi/3.)-2.;
289 r_c = r_c + omega * (1.5 + 2. * std::log((1. << 314 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) << 315 r_c = r_c - std::log(x)*(2.*std::log(x)-1.);
291 r_c = r_c + (3. * std::log(x) - 1. - 1. / x) << 316 r_c = r_c + (3.*std::log(x)-1.-1./x)*std::log(1.-x);
292 317
293 return r_c; 318 return r_c;
294 } 319 }
295 320