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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: EvtGen/EvtVVpipiMoxhay.hh | |
12 | // | |
13 | // Description: This model is based on the proposal by Tuan and Lipkin | |
14 | // (Phys.Lett.B206:349-353,1988) and the subsequent model | |
15 | // by Moxhay (Phys.Rev.D39:3497,1989) for the dipion spectrum | |
16 | // in Y(3S) -> pi+ pi- Y(1S). Please Note: in Moxhay's paper, | |
17 | // he wrote the fitted value of the parameter Im(B)/A as | |
18 | // -0.2983. However, using his quoted value leads to the wrong | |
19 | // spectrum. Changing the sign of his quoted Im(B)/A fixes the | |
20 | // shape and reproduces his result. Therefore, please pass | |
21 | // Im(B)/A = 0.2983 and Re(B)/A = 0.2196 to get the correct shape | |
22 | // based on his fit to the CLEO data. | |
23 | // | |
24 | // Example: | |
25 | // | |
26 | // Decay Upsilon(3S) | |
27 | // 1.0000 Upsilon pi+ pi- Y3STOY1SPIPIMOXHAY 0.2196 0.2983; | |
28 | // Enddecay | |
29 | // | |
30 | // --> the order of parameters is: Re(B)/A Im(B)/A | |
31 | // | |
32 | // Modification history: | |
33 | // | |
34 | // SEKULA November 02, 2007 Module created | |
35 | // | |
36 | //------------------------------------------------------------------------ | |
37 | ||
38 | ||
39 | #include "EvtGenBase/EvtPatches.hh" | |
40 | #include <stdlib.h> | |
41 | #include "EvtGenBase/EvtParticle.hh" | |
42 | #include "EvtGenBase/EvtGenKine.hh" | |
43 | #include "EvtGenBase/EvtPDL.hh" | |
44 | #include "EvtGenBase/EvtVector4C.hh" | |
45 | #include "EvtGenBase/EvtTensor4C.hh" | |
46 | #include "EvtGenBase/EvtReport.hh" | |
47 | #include "EvtGenModels/EvtY3SToY1SpipiMoxhay.hh" | |
48 | #include <string> | |
49 | using std::endl; | |
50 | ||
51 | EvtY3SToY1SpipiMoxhay::~EvtY3SToY1SpipiMoxhay() {} | |
52 | ||
53 | std::string EvtY3SToY1SpipiMoxhay::getName(){ | |
54 | ||
55 | return "Y3STOY1SPIPIMOXHAY"; | |
56 | ||
57 | } | |
58 | ||
59 | ||
60 | EvtDecayBase* EvtY3SToY1SpipiMoxhay::clone(){ | |
61 | ||
62 | return new EvtY3SToY1SpipiMoxhay; | |
63 | ||
64 | } | |
65 | ||
66 | void EvtY3SToY1SpipiMoxhay::init(){ | |
67 | ||
68 | static EvtId PIP=EvtPDL::getId("pi+"); | |
69 | static EvtId PIM=EvtPDL::getId("pi-"); | |
70 | static EvtId PI0=EvtPDL::getId("pi0"); | |
71 | ||
72 | // check that there are 2 arguments | |
73 | checkNArg(2); | |
74 | checkNDaug(3); | |
75 | ||
76 | checkSpinParent(EvtSpinType::VECTOR); | |
77 | checkSpinDaughter(0,EvtSpinType::VECTOR); | |
78 | ||
79 | ||
80 | ||
81 | if ((!(getDaug(1)==PIP&&getDaug(2)==PIM))&& | |
82 | (!(getDaug(1)==PI0&&getDaug(2)==PI0))) { | |
83 | report(ERROR,"EvtGen") << "EvtY3SToY1SpipiMoxhay generator expected " | |
84 | << " pi+ and pi- (or pi0 and pi0) " | |
85 | << "as 2nd and 3rd daughter. "<<endl; | |
86 | report(ERROR,"EvtGen") << "Will terminate execution!"<<endl; | |
87 | ::abort(); | |
88 | } | |
89 | ||
90 | } | |
91 | ||
92 | void EvtY3SToY1SpipiMoxhay::initProbMax() { | |
93 | setProbMax(0.2); | |
94 | } | |
95 | ||
96 | void EvtY3SToY1SpipiMoxhay::decay( EvtParticle *p){ | |
97 | ||
98 | p->initializePhaseSpace(getNDaug(),getDaugs()); | |
99 | ||
100 | EvtParticle *v,*s1,*s2; | |
101 | ||
102 | v=p->getDaug(0); | |
103 | s1=p->getDaug(1); | |
104 | s2=p->getDaug(2); | |
105 | ||
106 | ||
107 | // setup the parameters needed for this model | |
108 | double g_spp = 0.64; | |
109 | double lambda = -0.73; | |
110 | double m_sigma = 0.71; | |
111 | double f_pi = 0.094; | |
112 | double m_pi = s1->getP4().mass(); | |
113 | ||
114 | double MV1 = p->getP4().mass(); | |
115 | double MV2 = v->getP4().mass(); | |
116 | ||
117 | double q = (s1->getP4()+s2->getP4()).mass(); | |
118 | ||
119 | double EV2 = (MV1*MV1 - MV2*MV2 - q*q)/(2.0 * q); | |
120 | ||
121 | double ReB_over_A = getArg(0); | |
122 | double ImB_over_A = getArg(1); | |
123 | ||
124 | ||
125 | EvtComplex Xi; | |
126 | ||
127 | Xi = EvtComplex( 2.0/EvtConst::pi * ( 1.0 - sqrt(1.0 - 4*m_pi*m_pi/(q*q)) * log( (sqrt(q*q) + sqrt(q*q-4.0*m_pi*m_pi))/(2*m_pi) )), | |
128 | sqrt(1.0 - 4*m_pi*m_pi/(q*q))); | |
129 | ||
130 | // The form factor | |
131 | EvtComplex F; | |
132 | ||
133 | F = (g_spp*g_spp + lambda*(m_sigma*m_sigma - q*q)) / ( ( (m_sigma*m_sigma - q*q)*(1.0 - lambda*Xi) - (g_spp*g_spp*Xi) ) * 1.0/(8.0 * EvtConst::pi * f_pi*f_pi) * q * q ); | |
134 | ||
135 | EvtComplex B_over_A; | |
136 | B_over_A = EvtComplex(ReB_over_A, ImB_over_A); | |
137 | ||
138 | // The dGamma/d(M_pipi) spectrum | |
139 | EvtComplex dGdMpp; | |
140 | ||
141 | dGdMpp = abs2((q*q*F - B_over_A)) * q * sqrt(q*q - 4 * m_pi *m_pi) * sqrt(EV2 * EV2 - MV2*MV2); | |
142 | ||
143 | ||
144 | setProb( real(dGdMpp) ); | |
145 | return ; | |
146 | ||
147 | } | |
148 | ||
149 | ||
150 | ||
151 |