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da0e9ce3 | 1 | //-------------------------------------------------------------------------- |
2 | // | |
3 | // Environment: | |
4 | // This software is part of the EvtGen package developed jointly | |
5 | // for the BaBar and CLEO collaborations. If you use all or part | |
6 | // of it, please give an appropriate acknowledgement. | |
7 | // | |
8 | // Copyright Information: See EvtGen/COPYRIGHT | |
9 | // Copyright (C) 1998 Caltech, UCSB | |
10 | // | |
11 | // Module: EvtVll.cc | |
12 | // | |
13 | // Description: The decay of a vector meson to two leptons, | |
14 | // or generally, two spin 1/2 particles. | |
15 | // E.g., J/psi -> e+ e- | |
16 | // | |
17 | // Modification history: | |
18 | // | |
19 | // RYD January 17, 1997 Module created | |
20 | // | |
21 | //------------------------------------------------------------------------ | |
22 | // | |
23 | #include "EvtGenBase/EvtPatches.hh" | |
24 | #include <stdlib.h> | |
25 | #include <iostream> | |
26 | #include <string> | |
27 | #include "EvtGenBase/EvtParticle.hh" | |
28 | #include "EvtGenBase/EvtPDL.hh" | |
29 | #include "EvtGenBase/EvtGenKine.hh" | |
30 | #include "EvtGenModels/EvtVll.hh" | |
31 | #include "EvtGenBase/EvtDiracSpinor.hh" | |
32 | #include "EvtGenBase/EvtReport.hh" | |
33 | #include "EvtGenBase/EvtVector4C.hh" | |
34 | ||
35 | EvtVll::~EvtVll() {} | |
36 | ||
37 | std::string EvtVll::getName(){ | |
38 | ||
39 | return "VLL"; | |
40 | ||
41 | } | |
42 | ||
43 | ||
44 | EvtDecayBase* EvtVll::clone(){ | |
45 | ||
46 | return new EvtVll; | |
47 | ||
48 | } | |
49 | ||
50 | void EvtVll::init(){ | |
51 | ||
52 | // check that there are 0 arguments | |
53 | checkNArg(0); | |
54 | checkNDaug(2); | |
55 | ||
56 | checkSpinParent(EvtSpinType::VECTOR); | |
57 | ||
58 | checkSpinDaughter(0,EvtSpinType::DIRAC); | |
59 | checkSpinDaughter(1,EvtSpinType::DIRAC); | |
60 | ||
61 | } | |
62 | ||
63 | void EvtVll::initProbMax(){ | |
64 | ||
65 | setProbMax(1.0); | |
66 | ||
67 | } | |
68 | ||
69 | void EvtVll::decay(EvtParticle *p){ | |
70 | ||
71 | p->initializePhaseSpace(getNDaug(),getDaugs()); | |
72 | ||
73 | EvtParticle *l1, *l2; | |
74 | l1 = p->getDaug(0); | |
75 | l2 = p->getDaug(1); | |
76 | ||
77 | EvtVector4C l11, l12, l21, l22; | |
78 | l11=EvtLeptonVCurrent(l1->spParent(0),l2->spParent(0)); | |
79 | l12=EvtLeptonVCurrent(l1->spParent(0),l2->spParent(1)); | |
80 | l21=EvtLeptonVCurrent(l1->spParent(1),l2->spParent(0)); | |
81 | l22=EvtLeptonVCurrent(l1->spParent(1),l2->spParent(1)); | |
82 | ||
83 | EvtVector4C eps0=p->eps(0); | |
84 | EvtVector4C eps1=p->eps(1); | |
85 | EvtVector4C eps2=p->eps(2); | |
86 | ||
87 | double M2=p->mass(); | |
88 | M2*=M2; | |
89 | double m2=l1->mass(); | |
90 | m2*=m2; | |
91 | ||
92 | double norm=1.0/sqrt(2*M2+4*m2-4*m2*m2/M2); | |
93 | ||
94 | vertex(0,0,0,norm*(eps0*l11)); | |
95 | vertex(0,0,1,norm*(eps0*l12)); | |
96 | vertex(0,1,0,norm*(eps0*l21)); | |
97 | vertex(0,1,1,norm*(eps0*l22)); | |
98 | ||
99 | vertex(1,0,0,norm*(eps1*l11)); | |
100 | vertex(1,0,1,norm*(eps1*l12)); | |
101 | vertex(1,1,0,norm*(eps1*l21)); | |
102 | vertex(1,1,1,norm*(eps1*l22)); | |
103 | ||
104 | vertex(2,0,0,norm*(eps2*l11)); | |
105 | vertex(2,0,1,norm*(eps2*l12)); | |
106 | vertex(2,1,0,norm*(eps2*l21)); | |
107 | vertex(2,1,1,norm*(eps2*l22)); | |
108 | ||
109 | return; | |
110 | ||
111 | } | |
112 | ||
113 | ||
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