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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: EvtTauScalarnu.cc | |
12 | // | |
13 | // Description: The leptonic decay of the tau meson. | |
14 | // E.g., tau- -> e- nueb nut | |
15 | // | |
16 | // Modification history: | |
17 | // | |
18 | // RYD January 17, 1997 Module created | |
19 | // | |
20 | //------------------------------------------------------------------------ | |
21 | // | |
22 | #include "EvtGenBase/EvtPatches.hh" | |
23 | #include "EvtGenBase/EvtPatches.hh" | |
24 | #include <iostream> | |
25 | #include <string> | |
26 | #include "EvtGenBase/EvtParticle.hh" | |
27 | #include "EvtGenBase/EvtDiracParticle.hh" | |
28 | #include "EvtGenBase/EvtPDL.hh" | |
29 | #include "EvtGenBase/EvtIdSet.hh" | |
30 | #include "EvtGenBase/EvtGenKine.hh" | |
31 | #include "EvtGenModels/EvtBsquark.hh" | |
32 | #include "EvtGenBase/EvtDiracSpinor.hh" | |
33 | #include "EvtGenBase/EvtGammaMatrix.hh" | |
34 | #include "EvtGenBase/EvtReport.hh" | |
35 | ||
36 | EvtBsquark::~EvtBsquark() {} | |
37 | ||
38 | std::string EvtBsquark::getName(){ | |
39 | ||
40 | return "BSQUARK"; | |
41 | ||
42 | } | |
43 | ||
44 | ||
45 | EvtDecayBase* EvtBsquark::clone(){ | |
46 | ||
47 | return new EvtBsquark; | |
48 | ||
49 | } | |
50 | ||
51 | void EvtBsquark::init(){ | |
52 | ||
53 | // check that there are 5 arguments | |
54 | checkNArg(5); | |
55 | } | |
56 | ||
57 | void EvtBsquark::initProbMax(){ | |
58 | ||
59 | //For now do not set a maximum. | |
60 | ||
61 | //SetProbMax(0.000000000005); | |
62 | ||
63 | } | |
64 | ||
65 | void EvtBsquark::decay(EvtParticle *p){ | |
66 | ||
67 | static EvtId cquark=EvtPDL::getId("c"); | |
68 | static EvtId anticquark=EvtPDL::getId("anti-c"); | |
69 | ||
70 | static EvtIdSet leptons("e-","mu-","tau-"); | |
71 | ||
72 | p->initializePhaseSpace(getNDaug(),getDaugs()); | |
73 | ||
74 | ||
75 | int charge=1; | |
76 | ||
77 | EvtParticle* lepton; | |
78 | lepton = p->getDaug(1); | |
79 | if (leptons.contains(lepton->getId())){ | |
80 | charge=-1; | |
81 | } | |
82 | ||
83 | ||
84 | EvtDiracParticle charmquark; | |
85 | ||
86 | //this is a very crude approximation... | |
87 | if (charge==-1){ | |
88 | charmquark.init(cquark,p->getDaug(0)->getP4()); | |
89 | } | |
90 | else{ | |
91 | charmquark.init(anticquark,p->getDaug(0)->getP4()); | |
92 | } | |
93 | ||
94 | EvtVector4R p4c = p->getDaug(0)->getP4(); | |
95 | ||
96 | EvtVector4R p4sn = p->getDaug(2)->getP4(); | |
97 | ||
98 | EvtVector4R p4b(p->mass(),0.0,0.0,0.0); | |
99 | ||
100 | EvtComplex M[2][2]; | |
101 | ||
102 | int il,ic; | |
103 | ||
104 | //project out the right handed current | |
105 | EvtGammaMatrix PR=0.5*(EvtGammaMatrix::id()+EvtGammaMatrix::g5()); | |
106 | ||
107 | double tanbeta=getArg(1); | |
108 | double cosbeta=cos(atan(tanbeta)); | |
109 | double sinbeta=sin(atan(tanbeta)); | |
110 | ||
111 | double mb=4.9; | |
112 | double mc=1.3; | |
113 | double mw=80.4; | |
114 | ||
115 | double Mass=getArg(2); | |
116 | double mu=getArg(3); | |
117 | double mchargino=getArg(4); | |
118 | ||
119 | ||
120 | double tan2phim=2*sqrt(2.0)*mw*(mu*cosbeta+Mass*sinbeta)/ | |
121 | (Mass*Mass-mu*mu+2*mw*mw*cos(2*atan(tanbeta))); | |
122 | ||
123 | double phim=0.5*atan(tan2phim); | |
124 | ||
125 | EvtComplex U11=cos(phim); | |
126 | EvtComplex U12=sin(phim); | |
127 | EvtComplex U21=-sin(phim); | |
128 | EvtComplex U22=cos(phim); | |
129 | ||
130 | double tan2phip=2*sqrt(2.0)*mw*(mu*cosbeta+Mass*sinbeta)/ | |
131 | (Mass*Mass-mu*mu-2*mw*mw*cos(2*atan(tanbeta))); | |
132 | ||
133 | double phip=0.5*atan(tan2phip); | |
134 | ||
135 | EvtComplex V11=cos(phip); | |
136 | EvtComplex V12=sin(phip); | |
137 | EvtComplex V21=-sin(phip); | |
138 | EvtComplex V22=cos(phip); | |
139 | ||
140 | ||
141 | double theta=getArg(0); | |
142 | double ctheta=cos(theta); | |
143 | double stheta=sin(theta); | |
144 | ||
145 | double vcsb=0.08; | |
146 | double mchi1=mchargino; | |
147 | double mchi2=mchargino; | |
148 | ||
149 | //overall scale factor | |
150 | double g=1.0; | |
151 | ||
152 | EvtComplex a1=mchi1*(U11*ctheta-mb*U12*stheta/(sqrt(2.0)*mw*cosbeta)); | |
153 | EvtComplex a2=mchi2*(U21*ctheta-mb*U22*stheta/(sqrt(2.0)*mw*cosbeta)); | |
154 | ||
155 | EvtComplex b1=mc*conj(V12)*ctheta/(sqrt(2.0)*mw*sinbeta); | |
156 | EvtComplex b2=mc*conj(V22)*ctheta/(sqrt(2.0)*mw*sinbeta); | |
157 | ||
158 | EvtComplex f1=-(g*g*V11*vcsb)/((p4b-p4c).mass2()-mchi1*mchi1); | |
159 | EvtComplex f2=-(g*g*V21*vcsb)/((p4b-p4c).mass2()-mchi1*mchi2); | |
160 | ||
161 | //report(INFO,"EvtGen") <<g<<" "<<V11<<" "<<FL<<" "<<vcsb<<" "<<mchi1<<endl; | |
162 | //report(INFO,"EvtGen") << "f1:"<<f1<<" "<<(p4b-p4c).mass2()<<endl; | |
163 | //report(INFO,"EvtGen") << "f2:"<<f2<<" "<<(p4b-p4c).mass2()<<endl; | |
164 | ||
165 | //report(INFO,"EvtGen") << "p4sn:"<<p4sn<<endl; | |
166 | ||
167 | EvtGammaMatrix pslash=p4sn.get(0)*EvtGammaMatrix::g0() | |
168 | -p4sn.get(1)*EvtGammaMatrix::g1() | |
169 | -p4sn.get(2)*EvtGammaMatrix::g2() | |
170 | -p4sn.get(3)*EvtGammaMatrix::g3(); | |
171 | ||
172 | //report(INFO,"EvtGen") << "pslash:"<<pslash<<endl; | |
173 | ||
174 | ||
175 | ||
176 | for(il=0;il<2;il++){ | |
177 | for(ic=0;ic<2;ic++){ | |
178 | ||
179 | EvtComplex a=0.0; | |
180 | EvtComplex b=0.0; | |
181 | ||
182 | if (charge==-1){ | |
183 | a=charmquark.spParent(ic)*(PR*lepton->spParent(il)); | |
184 | b=charmquark.spParent(ic)*((pslash*PR)*lepton->spParent(il)); | |
185 | } | |
186 | else{ | |
187 | a=lepton->spParent(il)*(PR*charmquark.spParent(ic)); | |
188 | b=lepton->spParent(il)*((pslash*PR)*charmquark.spParent(ic)); | |
189 | } | |
190 | ||
191 | //report(INFO,"EvtGen") <<"pslash*PR:"<<pslash*PR<<endl; | |
192 | //report(INFO,"EvtGen") <<"sp charm:"<<charmquark.spParent(ic)<<endl; | |
193 | //report(INFO,"EvtGen") <<"sp lepton:"<<lepton->spParent(il)<<endl; | |
194 | ||
195 | M[ic][il]=f1*(a1*a+b1*b)+f2*(a2*a+b2*b); | |
196 | ||
197 | //report(INFO,"EvtGen") << "Contr1:"<<a1<<" "<<a<<" "<<b1<<" "<<b<<endl; | |
198 | //report(INFO,"EvtGen") << "Contr2:"<<a2<<" "<<a<<" "<<b2<<" "<<b<<endl; | |
199 | ||
200 | //report(INFO,"EvtGen") <<"case1:"<<f1<<" "<<a1<<" "<<b1<<" "<<a<<" "<<b<<endl; | |
201 | //report(INFO,"EvtGen") <<"case2:"<<f2<<" "<<a2<<" "<<b2<<" "<<a<<" "<<b<<endl; | |
202 | ||
203 | } | |
204 | } | |
205 | ||
206 | double prob=real(M[0][0]*conj(M[0][0])+ | |
207 | M[1][0]*conj(M[1][0])+ | |
208 | M[0][1]*conj(M[0][1])+ | |
209 | M[1][1]*conj(M[1][1])); | |
210 | ||
211 | //report(INFO,"EvtGen") <<"prob:"<<prob<<endl; | |
212 | ||
213 | setProb(prob); | |
214 | ||
215 | return; | |
216 | ||
217 | } | |
218 |