source: trunk/source/particles/management/src/G4MuonRadiativeDecayChannelWithSpin.cc@ 1303

Last change on this file since 1303 was 1196, checked in by garnier, 16 years ago

update CVS release candidate geant4.9.3.01
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[824]1//
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24// ********************************************************************
25//
26// ------------------------------------------------------------
27// GEANT 4 class header file
28//
29// History:
30// 01 August 2007 P.Gumplinger
31// Reference: TRIUMF TWIST Technotes TN-55:
32// Pierre Depommier - "Radiative MuonDecay"
33//
34// ------------------------------------------------------------
35//
36//
37//
38
39#include "G4MuonRadiativeDecayChannelWithSpin.hh"
40
41#include "Randomize.hh"
42#include "G4DecayProducts.hh"
43#include "G4LorentzVector.hh"
44
45G4MuonRadiativeDecayChannelWithSpin::
46 G4MuonRadiativeDecayChannelWithSpin(const G4String& theParentName,
47 G4double theBR)
48 : G4VDecayChannel("Radiative Muon Decay",1)
49{
50 // set names for daughter particles
51 if (theParentName == "mu+") {
52 SetBR(theBR);
53 SetParent("mu+");
54 SetNumberOfDaughters(4);
55 SetDaughter(0, "e+");
56 SetDaughter(1, "gamma");
57 SetDaughter(2, "nu_e");
58 SetDaughter(3, "anti_nu_mu");
59 } else if (theParentName == "mu-") {
60 SetBR(theBR);
61 SetParent("mu-");
62 SetNumberOfDaughters(4);
63 SetDaughter(0, "e-");
64 SetDaughter(1, "gamma");
65 SetDaughter(2, "anti_nu_e");
66 SetDaughter(3, "nu_mu");
67 } else {
68#ifdef G4VERBOSE
69 if (GetVerboseLevel()>0) {
70 G4cout << "G4RadiativeMuonDecayChannel:: constructor :";
71 G4cout << " parent particle is not muon but ";
72 G4cout << theParentName << G4endl;
73 }
74#endif
75 }
76}
77
78G4MuonRadiativeDecayChannelWithSpin::~G4MuonRadiativeDecayChannelWithSpin()
79{
80}
81
82G4DecayProducts *G4MuonRadiativeDecayChannelWithSpin::DecayIt(G4double)
83{
84
85#ifdef G4VERBOSE
86 if (GetVerboseLevel()>1)
87 G4cout << "G4MuonRadiativeDecayChannelWithSpin::DecayIt ";
88#endif
89
90 if (parent == 0) FillParent();
91 if (daughters == 0) FillDaughters();
92
93 // parent mass
94 G4double parentmass = parent->GetPDGMass();
95
96 EMMU = parentmass;
97
98 //daughters'mass
99 G4double daughtermass[4];
100 G4double sumofdaughtermass = 0.0;
101 for (G4int index=0; index<4; index++){
102 daughtermass[index] = daughters[index]->GetPDGMass();
103 sumofdaughtermass += daughtermass[index];
104 }
105
106 EMASS = daughtermass[0];
107
108 //create parent G4DynamicParticle at rest
109 G4ThreeVector dummy;
110 G4DynamicParticle * parentparticle =
111 new G4DynamicParticle( parent, dummy, 0.0);
112 //create G4Decayproducts
113 G4DecayProducts *products = new G4DecayProducts(*parentparticle);
114 delete parentparticle;
115
116 G4int i = 0;
117
118 G4double eps = EMASS/EMMU;
119
120 G4double som0, Qsqr, x, y, xx, yy, zz;
121 G4double cthetaE, cthetaG, cthetaGE, phiE, phiG;
122
123 do {
124
125// leap1:
126
127 i++;
128
129// leap2:
130
131 do {
132//
133//--------------------------------------------------------------------------
134// Build two vectors of random length and random direction, for the
135// positron and the photon.
136// x/y is the length of the vector, xx, yy and zz the components,
137// phi is the azimutal angle, theta the polar angle.
138//--------------------------------------------------------------------------
139//
140// For the positron
141//
142 x = G4UniformRand();
143
144 rn3dim(xx,yy,zz,x);
145
[1196]146 if(std::fabs((xx*xx)+(yy*yy)+(zz*zz)-(x*x))>0.001){
[824]147 G4cout << "Norm of x not correct" << G4endl;
148 }
149
150 phiE = atan4(xx,yy);
151 cthetaE = zz/x;
152 G4double sthetaE = std::sqrt((xx*xx)+(yy*yy))/x;
153//
154// What you get:
155//
156// x = positron energy
157// phiE = azimutal angle of positron momentum
158// cthetaE = cosine of polar angle of positron momentum
159// sthetaE = sine of polar angle of positron momentum
160//
161//// G4cout << " x, xx, yy, zz " << x << " " << xx << " "
162//// << yy << " " << zz << G4endl;
163//// G4cout << " phiE, cthetaE, sthetaE " << phiE << " "
164//// << cthetaE << " "
165//// << sthetaE << " " << G4endl;
166//
167//-----------------------------------------------------------------------
168//
169// For the photon
170//
171 y = G4UniformRand();
172
173 rn3dim(xx,yy,zz,y);
174
[1196]175 if(std::fabs((xx*xx)+(yy*yy)+(zz*zz)-(y*y))>0.001){
[824]176 G4cout << " Norm of y not correct " << G4endl;
177 }
178
179 phiG = atan4(xx,yy);
180 cthetaG = zz/y;
181 G4double sthetaG = std::sqrt((xx*xx)+(yy*yy))/y;
182//
183// What you get:
184//
185// y = photon energy
186// phiG = azimutal angle of photon momentum
187// cthetaG = cosine of polar angle of photon momentum
188// sthetaG = sine of polar angle of photon momentum
189//
190//// G4cout << " y, xx, yy, zz " << y << " " << xx << " "
191//// << yy << " " << zz << G4endl;
192//// G4cout << " phiG, cthetaG, sthetaG " << phiG << " "
193//// << cthetaG << " "
194//// << sthetaG << " " << G4endl;
195//
196//-----------------------------------------------------------------------
197//
198// Maybe certain restrictions on the kinematical variables:
199//
200//// if (cthetaE > 0.01)goto leap2;
201//// if (cthetaG > 0.01)goto leap2;
[1196]202//// if (std::fabs(x-0.5) > 0.5 )goto leap2;
203//// if (std::fabs(y-0.5) > 0.5 )goto leap2;
[824]204//
205//-----------------------------------------------------------------------
206//
207// Calculate the angle between positron and photon (cosine)
208//
209 cthetaGE = cthetaE*cthetaG+sthetaE*sthetaG*std::cos(phiE-phiG);
210//
211//// G4cout << x << " " << cthetaE << " " << sthetaE << " "
212//// << y << " " << cthetaG << " " << sthetaG << " "
213//// << cthetaGE
214//
215//-----------------------------------------------------------------------
216//
217 G4double term0 = eps*eps;
218 G4double term1 = x*((1.0-eps)*(1.0-eps))+2.0*eps;
219 G4double beta = std::sqrt( x*((1.0-eps)*(1.0-eps))*
220 (x*((1.0-eps)*(1.0-eps))+4.0*eps))/term1;
221 G4double delta = 1.0-beta*cthetaGE;
222
223 G4double term3 = y*(1.0-(eps*eps));
224 G4double term6 = term1*delta*term3;
225
226 Qsqr = (1.0-term1-term3+term0+0.5*term6)/((1.0-eps)*(1.0-eps));
227//
228//-----------------------------------------------------------------------
229//
230// Check the kinematics.
231//
232 } while ( Qsqr<0.0 || Qsqr>1.0 );
233//
234//// G4cout << x << " " << y << " " << beta << " " << Qsqr << G4endl;
235//
236// Do the calculation for -1 muon polarization (i.e. mu+)
237//
238 G4double Pmu = -1.0;
239 if (GetParentName() == "mu-")Pmu = +1.0;
240//
241// and for Fronsdal
242//
243//-----------------------------------------------------------------------
244//
245 som0 = fron(Pmu,x,y,cthetaE,cthetaG,cthetaGE);
246//
247//// if(som0<0.0){
248//// G4cout << " som0 < 0 in Fronsdal " << som0
249//// << " at event " << i << G4endl;
250//// G4cout << Pmu << " " << x << " " << y << " "
251//// << cthetaE << " " << cthetaG << " "
252//// << cthetaGE << " " << som0 << G4endl;
253//// }
254//
255//-----------------------------------------------------------------------
256//
257//// G4cout << x << " " << y << " " << som0 << G4endl;
258//
259//----------------------------------------------------------------------
260//
261// Sample the decay rate
262//
263
264 } while (G4UniformRand()*250000.0 > som0);
265
266/// if(i<10000000)goto leap1:
267//
268//-----------------------------------------------------------------------
269//
270 G4double E = EMMU/2.*(x*((1.-eps)*(1.-eps))+2.*eps);
271 G4double G = EMMU/2.*y*(1.-eps*eps);
272//
273//-----------------------------------------------------------------------
274//
275
276 if(E < EMASS) E = EMASS;
277
278 // calculate daughter momentum
279 G4double daughtermomentum[4];
280
281 daughtermomentum[0] = std::sqrt(E*E - EMASS*EMASS);
282
283 G4double sthetaE = std::sqrt(1.-cthetaE*cthetaE);
284 G4double cphiE = std::cos(phiE);
285 G4double sphiE = std::sin(phiE);
286
287 //Coordinates of the decay positron with respect to the muon spin
288
289 G4double px = sthetaE*cphiE;
290 G4double py = sthetaE*sphiE;
291 G4double pz = cthetaE;
292
293 G4ThreeVector direction0(px,py,pz);
294
295 direction0.rotateUz(parent_polarization);
296
297 G4DynamicParticle * daughterparticle0
298 = new G4DynamicParticle( daughters[0], daughtermomentum[0]*direction0);
299
300 products->PushProducts(daughterparticle0);
301
302 daughtermomentum[1] = G;
303
304 G4double sthetaG = std::sqrt(1.-cthetaG*cthetaG);
305 G4double cphiG = std::cos(phiG);
306 G4double sphiG = std::sin(phiG);
307
308 //Coordinates of the decay gamma with respect to the muon spin
309
310 px = sthetaG*cphiG;
311 py = sthetaG*sphiG;
312 pz = cthetaG;
313
314 G4ThreeVector direction1(px,py,pz);
315
316 direction1.rotateUz(parent_polarization);
317
318 G4DynamicParticle * daughterparticle1
319 = new G4DynamicParticle( daughters[1], daughtermomentum[1]*direction1);
320
321 products->PushProducts(daughterparticle1);
322
323 // daughter 3 ,4 (neutrinos)
324 // create neutrinos in the C.M frame of two neutrinos
325
326 G4double energy2 = parentmass*(1.0 - (x+y)/2.0);
327
328 G4double vmass = std::sqrt((energy2-
329 (daughtermomentum[0]+daughtermomentum[1]))*
330 (energy2+
331 (daughtermomentum[0]+daughtermomentum[1])));
[1196]332 G4double beta = (daughtermomentum[0]+daughtermomentum[1])/energy2;
333 beta = -1.0 * std::min(beta,0.99);
[824]334
335 G4double costhetan = 2.*G4UniformRand()-1.0;
336 G4double sinthetan = std::sqrt((1.0-costhetan)*(1.0+costhetan));
337 G4double phin = twopi*G4UniformRand()*rad;
338 G4double sinphin = std::sin(phin);
339 G4double cosphin = std::cos(phin);
340
341 G4ThreeVector direction2(sinthetan*cosphin,sinthetan*sinphin,costhetan);
342
343 G4DynamicParticle * daughterparticle2
344 = new G4DynamicParticle( daughters[2], direction2*(vmass/2.));
345 G4DynamicParticle * daughterparticle3
346 = new G4DynamicParticle( daughters[3], direction2*(-1.0*vmass/2.));
347
348 // boost to the muon rest frame
349
[1196]350 G4ThreeVector direction34(direction0.x()+direction1.x(),
351 direction0.y()+direction1.y(),
352 direction0.z()+direction1.z());
353 direction34 = direction34.unit();
[824]354
[1196]355 G4LorentzVector p4 = daughterparticle2->Get4Momentum();
356 p4.boost(direction34.x()*beta,direction34.y()*beta,direction34.z()*beta);
[824]357 daughterparticle2->Set4Momentum(p4);
[1196]358
[824]359 p4 = daughterparticle3->Get4Momentum();
[1196]360 p4.boost(direction34.x()*beta,direction34.y()*beta,direction34.z()*beta);
[824]361 daughterparticle3->Set4Momentum(p4);
362
363 products->PushProducts(daughterparticle2);
364 products->PushProducts(daughterparticle3);
365
366 daughtermomentum[2] = daughterparticle2->GetTotalMomentum();
367 daughtermomentum[3] = daughterparticle3->GetTotalMomentum();
368
369// output message
370#ifdef G4VERBOSE
371 if (GetVerboseLevel()>1) {
372 G4cout << "G4MuonRadiativeDecayChannelWithSpin::DecayIt ";
373 G4cout << " create decay products in rest frame " <<G4endl;
374 products->DumpInfo();
375 }
376#endif
377 return products;
378}
379
380G4double G4MuonRadiativeDecayChannelWithSpin::fron(G4double Pmu,
381 G4double x,
382 G4double y,
383 G4double cthetaE,
384 G4double cthetaG,
385 G4double cthetaGE)
386{
387 G4double mu = 105.65;
388 G4double me = 0.511;
389 G4double rho = 0.75;
390 G4double del = 0.75;
391 G4double eps = 0.0;
392 G4double kap = 0.0;
393 G4double ksi = 1.0;
394
395 G4double delta = 1-cthetaGE;
396
397// Calculation of the functions f(x,y)
398
399 G4double f_1s = 12.0*((y*y)*(1.0-y)+x*y*(2.0-3.0*y)
400 +2.0*(x*x)*(1.0-2.0*y)-2.0*(x*x*x));
401 G4double f0s = 6.0*(-x*y*(2.0-3.0*(y*y))
402 -2.0*(x*x)*(1.0-y-3.0*(y*y))+2.0*(x*x*x)*(1.0+2.0*y));
403 G4double f1s = 3.0*((x*x)*y*(2.0-3.0*y-3.0*(y*y))
404 -(x*x*x)*y*(4.0+3.0*y));
405 G4double f2s = 1.5*((x*x*x)*(y*y)*(2.0+y));
406
407 G4double f_1se = 12.0*(x*y*(1.0-x)+(x*x)*(2.0-3.0*y)
408 -2.0*(x*x*x));
409 G4double f0se = 6.0*(-(x*x)*(2.0-y-2.0*(y*y))
410 +(x*x*x)*(2.0+3.0*y));
411 G4double f1se = -3.0*(x*x*x)*y*(2.0+y);
412 G4double f2se = 0.0;
413
414 G4double f_1sg = 12.0*((y*y)*(1.0-y)+x*y*(1.0-2.0*y)
415 -(x*x)*y);
416 G4double f0sg = 6.0*(-x*(y*y)*(2.0-3.0*y)-(x*x)*y*(1.0-4.0*y)
417 +(x*x*x)*y);
418 G4double f1sg = 3.0*((x*x)*(y*y)*(1.0-3.0*y)
419 -2.0*(x*x*x)*(y*y));
420 G4double f2sg = 1.5*(x*x*x)*(y*y*y);
421
422 G4double f_1v = 8.0*((y*y)*(3.0-2.0*y)+6.0*x*y*(1.0-y)
423 +2.0*(x*x)*(3.0-4.0*y)-4.0*(x*x*x));
424 G4double f0v = 8.0*(-x*y*(3.0-y-(y*y))-(x*x)*(3.0-y-4.0*(y*y))
425 +2.0*(x*x*x)*(1.0+2.0*y));
426 G4double f1v = 2.0*((x*x)*y*(6.0-5.0*y-2.0*(y*y))
427 -2.0*(x*x*x)*y*(4.0+3.0*y));
428 G4double f2v = 2.0*(x*x*x)*(y*y)*(2.0+y);
429
430 G4double f_1ve = 8.0*(x*y*(1.0-2.0*y)
431 +2.0*(x*x)*(1.0-3.0*y)-4.0*(x*x*x));
432 G4double f0ve = 4.0*(-(x*x)*(2.0-3.0*y-4.0*(y*y))
433 +2.0*(x*x*x)*(2.0+3.0*y));
434 G4double f1ve = -4.0*(x*x*x)*y*(2.0+y);
435 G4double f2ve = 0.0;
436
437 G4double f_1vg = 8.0*((y*y)*(1.0-2.0*y)+x*y*(1.0-4.0*y)
438 -2.0*(x*x)*y);
439 G4double f0vg = 4.0*(2.0*x*(y*y)*(1.0+y)-(x*x)*y*(1.0-4.0*y)
440 +2.0*(x*x*x)*y);
441 G4double f1vg = 2.0*((x*x)*(y*y)*(1.0-2.0*y)
442 -4.0*(x*x*x)*(y*y));
443 G4double f2vg = 2.0*(x*x*x)*(y*y*y);
444
445 G4double f_1t = 8.0*((y*y)*(3.0-y)+3.0*x*y*(2.0-y)
446 +2.0*(x*x)*(3.0-2.0*y)-2.0*(x*x*x));
447 G4double f0t = 4.0*(-x*y*(6.0+(y*y))
448 -2.0*(x*x)*(3.0+y-3.0*(y*y))+2.0*(x*x*x)*(1.0+2.0*y));
449 G4double f1t = 2.0*((x*x)*y*(6.0-5.0*y+(y*y))
450 -(x*x*x)*y*(4.0+3.0*y));
451 G4double f2t = (x*x*x)*(y*y)*(2.0+y);
452
453 G4double f_1te = -8.0*(x*y*(1.0+3.0*y)+(x*x)*(2.0+3.0*y)
454 +2.0*(x*x*x));
455 G4double f0te = 4.0*((x*x)*(2.0+3.0*y+4.0*(y*y))
456 +(x*x*x)*(2.0+3.0*y));
457 G4double f1te = -2.0*(x*x*x)*y*(2.0+y);
458 G4double f2te = 0.0;
459
460 G4double f_1tg = -8.0*((y*y)*(1.0+y)+x*y+(x*x)*y);
461 G4double f0tg = 4.0*(x*(y*y)*(2.0-y)+(x*x)*y*(1.0+2.0*y)
462 +(x*x*x)*y);
463 G4double f1tg = -2.0*((x*x)*(y*y)*(1.0-y)+2.0*(x*x*x)*y);
464 G4double f2tg = (x*x*x)*(y*y*y);
465
466 G4double term = delta+2.0*(me*me)/((mu*mu)*(x*x));
467 term = 1.0/term;
468
469 G4double ns = term*f_1s+f0s+delta*f1s+(delta*delta)*f2s;
470 G4double nv = term*f_1v+f0v+delta*f1v+(delta*delta)*f2v;
471 G4double nt = term*f_1t+f0t+delta*f1t+(delta*delta)*f2t;
472
473 G4double nse = term*f_1se+f0se+delta*f1se+(delta*delta)*f2se;
474 G4double nve = term*f_1ve+f0ve+delta*f1ve+(delta*delta)*f2ve;
475 G4double nte = term*f_1te+f0te+delta*f1te+(delta*delta)*f2te;
476
477 G4double nsg = term*f_1sg+f0sg+delta*f1sg+(delta*delta)*f2sg;
478 G4double nvg = term*f_1vg+f0vg+delta*f1vg+(delta*delta)*f2vg;
479 G4double ntg = term*f_1tg+f0tg+delta*f1tg+(delta*delta)*f2tg;
480
481 G4double term1 = nv;
482 G4double term2 = 2.0*ns-nv-nt;
483 G4double term3 = 2.0*ns-2.0*nv+nt;
484
485 G4double term1e = 1.0/3.0*(1.0-4.0/3.0*del);
486 G4double term2e = 2.0*nse+5.0*nve-nte;
487 G4double term3e = 2.0*nse-2.0*nve+nte;
488
489 G4double term1g = 1.0/3.0*(1.0-4.0/3.0*del);
490 G4double term2g = 2.0*nsg+5.0*nvg-ntg;
491 G4double term3g = 2.0*nsg-2.0*nvg+ntg;
492
493 G4double som00 = term1+(1.0-4.0/3.0*rho)*term2+eps*term3;
494 G4double som01 = -Pmu*ksi*(cthetaE*(nve-term1e*term2e+kap*term3e)
495 +cthetaG*(nvg-term1g*term2g+kap*term3g));
496 G4double som0 = som00+som01;
497
498// G4cout << x << " " << y << " " << som00 << " "
499// << som01 << " " << som0 << G4endl;
500
501 return som0;
502}
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