]>
Commit | Line | Data |
---|---|---|
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) 2000 Caltech, UCSB | |
10 | // | |
11 | // Module: EvtdFunctionSingle.cc | |
12 | // | |
13 | // Description: Evaluates one Wigner d-Functions. | |
14 | // | |
15 | // Modification history: | |
16 | // | |
17 | // fkw February 2, 2001 changes to satisfy KCC | |
18 | // RYD August 10, 2000 Module created | |
19 | // | |
20 | //------------------------------------------------------------------------ | |
21 | // | |
22 | #include "EvtGenBase/EvtPatches.hh" | |
23 | #include <stdlib.h> | |
24 | #include <math.h> | |
25 | #include <iostream> | |
26 | #include <assert.h> | |
27 | #include "EvtGenBase/EvtdFunctionSingle.hh" | |
28 | ||
29 | EvtdFunctionSingle::EvtdFunctionSingle(){ | |
30 | _j=0; | |
31 | _m1=0; | |
32 | _m2=0; | |
33 | _coef=0; | |
34 | _kmin=0; | |
35 | _kmax=0; | |
36 | } | |
37 | ||
38 | ||
39 | EvtdFunctionSingle::~EvtdFunctionSingle(){ | |
40 | if (_coef!=0) delete [] _coef; | |
41 | } | |
42 | ||
43 | ||
44 | void EvtdFunctionSingle::init(int j,int m1,int m2){ | |
45 | ||
46 | assert(abs(m2)>=abs(m1)); | |
47 | assert(m2>=0); | |
48 | ||
49 | _j=j; | |
50 | _m1=m1; | |
51 | _m2=m2; | |
52 | ||
53 | _kmin=_m2-_m1; | |
54 | _kmax=_j-_m1; | |
55 | ||
56 | assert(_kmin<=_kmax); | |
57 | ||
58 | _coef=new double[(_kmax-_kmin)/2+1]; | |
59 | ||
60 | int k; | |
61 | ||
62 | for(k=_kmin;k<=_kmax;k+=2){ | |
63 | int sign=1; | |
64 | if ((k-_m2+_m1)%4!=0) sign=-sign; | |
65 | double tmp = fact((_j+_m2)/2)*fact((_j-_m2)/2) | |
66 | *fact((_j+_m1)/2)*fact((_j-_m1)/2); | |
67 | _coef[(k-_kmin)/2]=sign*sqrt(tmp)/ | |
68 | (fact((_j+_m2-k)/2)*fact(k/2)*fact((_j-_m1-k)/2)*fact((k-_m2+_m1)/2)); | |
69 | ||
70 | } | |
71 | ||
72 | } | |
73 | ||
74 | ||
75 | double EvtdFunctionSingle::d(int j,int m1,int m2, double theta){ | |
76 | ||
0ca57c2f | 77 | assert(j==_j); _unused( j ); |
da0e9ce3 | 78 | assert(m1==_m1); |
79 | assert(m2==_m2); | |
80 | ||
81 | double c2=cos(0.5*theta); | |
82 | double s2=sin(0.5*theta); | |
83 | ||
84 | double d=0.0; | |
85 | ||
86 | int k; | |
87 | for(k=_kmin;k<=_kmax;k+=2){ | |
88 | d+=_coef[(k-_kmin)/2]*pow(c2,(2*_j-2*k+m2-m1)/2)*pow(s2,(2*k-m2+m1)/2); | |
89 | } | |
90 | ||
91 | return d; | |
92 | ||
93 | } | |
94 | ||
95 | ||
96 | int EvtdFunctionSingle::fact(int n){ | |
97 | ||
98 | assert(n>=0); | |
99 | ||
100 | int f=1; | |
101 | ||
102 | int k; | |
103 | for(k=2;k<=n;k++) f*=k; | |
104 | ||
105 | return f; | |
106 | ||
107 | } | |
108 | ||
109 | ||
110 |