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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: EvtPhotonParticle.cc | |
12 | // | |
13 | // Description: Class to describe massless vectors | |
14 | // | |
15 | // Modification history: | |
16 | // | |
17 | // DJL/RYD September 25, 1996 Module created | |
18 | // | |
19 | //------------------------------------------------------------------------ | |
20 | // | |
21 | #include "EvtGenBase/EvtPatches.hh" | |
22 | #include <stdlib.h> | |
23 | #include <iostream> | |
24 | #include <math.h> | |
25 | #include "EvtGenBase/EvtComplex.hh" | |
26 | #include "EvtGenBase/EvtPhotonParticle.hh" | |
27 | #include "EvtGenBase/EvtVector4C.hh" | |
28 | #include "EvtGenBase/EvtReport.hh" | |
29 | using std::endl; | |
30 | ||
31 | EvtPhotonParticle::~EvtPhotonParticle(){} | |
32 | ||
33 | void EvtPhotonParticle::init(EvtId part_n,const EvtVector4R& p4){ | |
34 | ||
35 | init(part_n,p4.get(0),p4.get(1), | |
36 | p4.get(2),p4.get(3)); | |
37 | } | |
38 | ||
39 | void EvtPhotonParticle::init(EvtId part_n,double e,double px,double py,double pz){ | |
40 | ||
41 | _validP4=true; | |
42 | setp(e,px,py,pz); | |
43 | setpart_num(part_n); | |
44 | ||
45 | setLifetime(); | |
46 | ||
47 | //defere calculation of basis vectors untill they are needed! | |
48 | _evalBasis=0; | |
49 | ||
50 | } | |
51 | ||
52 | ||
53 | EvtVector4C EvtPhotonParticle::epsParentPhoton(int i){ | |
54 | ||
55 | if (!_evalBasis){ | |
56 | ||
57 | _evalBasis=1; | |
58 | eps1.set(EvtComplex(0.0,0.0), EvtComplex(-1.0/sqrt(2.0),0.0), | |
59 | EvtComplex(0.0,-1.0/sqrt(2.0)), EvtComplex(0.0,0.0)); | |
60 | eps2.set(EvtComplex(0.0,0.0), EvtComplex(1.0/sqrt(2.0),0.0), | |
61 | EvtComplex(0.0,-1.0/sqrt(2.0)), EvtComplex(0.0,0.0)); | |
62 | ||
63 | // These are for photon along z axis. Rotate to get | |
64 | // correct direction... | |
65 | ||
66 | double phi,theta; | |
67 | ||
68 | EvtVector4R p=this->getP4(); | |
69 | ||
70 | double px=p.get(1); | |
71 | double py=p.get(2); | |
72 | double pz=p.get(3); | |
73 | ||
74 | phi = atan2(py,px); | |
75 | theta = acos(pz/sqrt(px*px+py*py+pz*pz)); | |
76 | eps1.applyRotateEuler(phi,theta,-phi); | |
77 | eps2.applyRotateEuler(phi,theta,-phi); | |
78 | ||
79 | } | |
80 | ||
81 | ||
82 | EvtVector4C temp; | |
83 | ||
84 | switch(i) { | |
85 | ||
86 | case 0: | |
87 | temp=eps1; | |
88 | break; | |
89 | case 1: | |
90 | temp=eps2; | |
91 | break; | |
92 | default: | |
93 | report(ERROR,"EvtGen") << "EvtPhotonParticle.cc: Asked " | |
94 | << "for state:"<<i<<endl; | |
95 | ::abort(); | |
96 | break; | |
97 | } | |
98 | ||
99 | return temp; | |
100 | } | |
101 | ||
102 | EvtVector4C EvtPhotonParticle::epsPhoton(int ){ | |
103 | ||
104 | report(ERROR,"EvtGen") << "EvtPhotonParticle.cc: Can not get " | |
105 | << "state in photons restframe."<<endl;; | |
106 | ::abort(); | |
107 | return EvtVector4C(); | |
108 | ||
109 | } | |
110 | ||
111 | ||
112 | EvtSpinDensity EvtPhotonParticle::rotateToHelicityBasis() const { | |
113 | ||
114 | EvtVector4C eplus(0.0,-1.0/sqrt(2.0), | |
115 | EvtComplex(0.0,-1.0/sqrt(2.0)),0.0); | |
116 | EvtVector4C eminus(0.0,1.0/sqrt(2.0), | |
117 | EvtComplex(0.0,-1.0/sqrt(2.0)),0.0); | |
118 | ||
119 | //Really uggly have to cast away constness because the | |
120 | //function epsParentPhoton caches the state vectors... | |
121 | EvtVector4C e1=((EvtParticle*)this)->epsParentPhoton(0); | |
122 | EvtVector4C e2=((EvtParticle*)this)->epsParentPhoton(1); | |
123 | ||
124 | ||
125 | EvtSpinDensity R; | |
126 | R.setDim(2); | |
127 | ||
128 | R.set(0,0,(eplus.conj())*e1); | |
129 | R.set(0,1,(eplus.conj())*e2); | |
130 | ||
131 | R.set(1,0,(eminus.conj())*e1); | |
132 | R.set(1,1,(eminus.conj())*e2); | |
133 | ||
134 | return R; | |
135 | ||
136 | } | |
137 | ||
138 | ||
139 | EvtSpinDensity EvtPhotonParticle::rotateToHelicityBasis(double alpha, | |
140 | double beta, | |
141 | double gamma) const{ | |
142 | ||
143 | EvtVector4C eplus(0.0,-1.0/sqrt(2.0), | |
144 | EvtComplex(0.0,-1.0/sqrt(2.0)),0.0); | |
145 | EvtVector4C eminus(0.0,1.0/sqrt(2.0), | |
146 | EvtComplex(0.0,-1.0/sqrt(2.0)),0.0); | |
147 | ||
148 | eplus.applyRotateEuler(alpha,beta,gamma); | |
149 | eminus.applyRotateEuler(alpha,beta,gamma); | |
150 | ||
151 | ||
152 | //Really uggly have to cast away constness because the | |
153 | //function epsParentPhoton caches the state vectors... | |
154 | EvtVector4C e1=((EvtParticle*)this)->epsParentPhoton(0); | |
155 | EvtVector4C e2=((EvtParticle*)this)->epsParentPhoton(1); | |
156 | ||
157 | EvtSpinDensity R; | |
158 | R.setDim(2); | |
159 | ||
160 | R.set(0,0,(eplus.conj())*e1); | |
161 | R.set(0,1,(eplus.conj())*e2); | |
162 | ||
163 | R.set(1,0,(eminus.conj())*e1); | |
164 | R.set(1,1,(eminus.conj())*e2); | |
165 | ||
166 | return R; | |
167 | ||
168 | } | |
169 | ||
170 |