Line data Source code
1 : //-----------------------------------------------------------------------------------------------
2 : //
3 : // Module: EvtHypNonLepton.cpp
4 : //
5 : // Desription: Routine to implement Hyperon(s=1/2) -> Baryon(s=1/2) + Scalar decays accroding to
6 : // Review Of Particle Physics 2004, Phys.Lett.B, Vol.592, p.864
7 : //
8 : // Modification history:
9 : //
10 : // 09/02/2009 PR Corrected Delta sign
11 : // 20/02/2005 PR Module created according to PHSP and Lb2Lll model
12 : //
13 : //-----------------------------------------------------------------------------------------------
14 :
15 : #ifdef WIN32
16 : #pragma warning( disable : 4786 )
17 : // Disable anoying warning about symbol size
18 : #endif
19 :
20 : #include "EvtGenModels/EvtHypNonLepton.hh"
21 : #include "EvtGenBase/EvtParticle.hh"
22 : #include "EvtGenBase/EvtPDL.hh"
23 : #include "EvtGenBase/EvtDiracSpinor.hh"
24 : #include "EvtGenBase/EvtTensor4C.hh"
25 : #include "EvtGenBase/EvtVector4C.hh"
26 : #include "EvtGenBase/EvtVector4R.hh"
27 : #include "EvtGenBase/EvtComplex.hh"
28 : #include "EvtGenBase/EvtGammaMatrix.hh"
29 :
30 :
31 0 : EvtHypNonLepton::~EvtHypNonLepton() {}
32 :
33 : EvtDecayBase* EvtHypNonLepton::clone(){
34 0 : return new EvtHypNonLepton;
35 0 : }
36 :
37 : std::string EvtHypNonLepton::getName(){
38 0 : return "HypNonLepton";
39 : }
40 :
41 : void EvtHypNonLepton::init(){
42 :
43 0 : if(getNArg()<2 || getNArg()>3){ // alpha phi gamma delta
44 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton generator expected 2 or 3 arguments but found: " << getNArg() << std::endl;
45 0 : report(Severity::Info ,"EvtGen") << " 1. Decay asymmetry parameter - alpha" << std::endl;
46 0 : report(Severity::Info ,"EvtGen") << " 2. Parameter phi - in degrees (not radians)" << std::endl;
47 0 : report(Severity::Info ,"EvtGen") << " 3. Note on every x-th decay" << std::endl;
48 0 : ::abort();
49 : }
50 :
51 0 : if(getNDaug()!=2){ // Check that there are 2 daughters only
52 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton generator expected 2 daughters but found: " << getNDaug() << std::endl;
53 0 : ::abort();
54 : }
55 :
56 : // Check particles spins
57 0 : if(EvtSpinType::getSpin2(EvtPDL::getSpinType(getParentId()))!=1){
58 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton generator expected dirac parent particle, but found " << EvtSpinType::getSpin2(EvtPDL::getSpinType(getParentId())) << " spin degrees of freedom" << std::endl;
59 0 : ::abort();
60 : }
61 0 : if(EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(0)))!=1){
62 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton generator expected the first child to be dirac particle, but found " << EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(0))) << " spin degrees of freedom" << std::endl;
63 0 : ::abort();
64 : }
65 0 : if(EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(1)))!=0){
66 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton generator expected the second child to be scalar particle, but found " << EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(1))) << " spin degrees of freedom" << std::endl;
67 0 : ::abort();
68 : }
69 :
70 : // Read all parameters
71 0 : m_alpha = getArg(0);
72 0 : m_phi = getArg(1)*EvtConst::pi/180;
73 0 : if(getNArg()==3) m_noTries = static_cast<long>(getArg(2));
74 0 : else m_noTries = 0;
75 :
76 : // calculate additional parameters
77 : double p,M,m1,m2;
78 : double p_to_s,beta,delta,gamma;
79 :
80 0 : M = EvtPDL::getMass(getParentId());
81 0 : m1 = EvtPDL::getMass(getDaug(0));
82 0 : m2 = EvtPDL::getMass(getDaug(1));
83 :
84 0 : if(m1+m2>=M){
85 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton found impossible decay: " << M << " --> " << m1 << " + " << m2 << " GeV\n" << std::endl;
86 0 : ::abort();
87 : }
88 :
89 0 : p = sqrt(M*M-(m1+m2)*(m1+m2))*sqrt(M*M-(m1-m2)*(m1-m2))/2./M;
90 :
91 0 : beta = sqrt(1.-m_alpha*m_alpha)*sin(m_phi);
92 0 : delta = -atan2(beta,m_alpha);
93 0 : gamma = sqrt(1.-m_alpha*m_alpha-beta*beta);
94 0 : p_to_s = sqrt((1.-gamma)/(1.+gamma));
95 :
96 0 : m_B_to_A = p_to_s*(m1+sqrt(p*p+m1*m1))/p*EvtComplex(cos(delta),sin(delta));
97 :
98 0 : }
99 :
100 : void EvtHypNonLepton::initProbMax(){
101 :
102 : double maxProb,m1,m2,M,p;
103 :
104 0 : M=EvtPDL::getMass(getParentId());
105 0 : m1=EvtPDL::getMass(getDaug(0));
106 0 : m2=EvtPDL::getMass(getDaug(1));
107 :
108 0 : if(m1+m2>=M){
109 0 : report(Severity::Error,"EvtGen") << " ERROR: EvtHypNonLepton found impossible decay: " << M << " --> " << m1 << " + " << m2 << " GeV\n" << std::endl;
110 0 : ::abort();
111 : }
112 :
113 0 : p=sqrt(M*M-(m1+m2)*(m1+m2))*sqrt(M*M-(m1-m2)*(m1-m2))/2/M;
114 0 : maxProb=16*M*(sqrt(p*p+m1*m1)+m1+abs(m_B_to_A)*abs(m_B_to_A)*(sqrt(p*p+m1*m1)-m1));
115 : //maxProb *= G_F*M_pi*M_pi;
116 :
117 0 : setProbMax(maxProb);
118 0 : report(Severity::Info,"EvtGen") << " EvtHypNonLepton set up maximum probability to " << maxProb << std::endl;
119 :
120 0 : }
121 :
122 : void EvtHypNonLepton::decay(EvtParticle* parent){
123 :
124 0 : parent->initializePhaseSpace(getNDaug(),getDaugs());
125 0 : calcAmp(&_amp2,parent);
126 :
127 0 : }
128 :
129 : void EvtHypNonLepton::calcAmp(EvtAmp *amp,EvtParticle *parent){
130 :
131 : static long noTries=0;
132 : int i;
133 0 : EvtComplex Matrix[2][2];
134 :
135 : //G_F = 1.16637e-5;
136 : //M_pi = 0.13957;
137 :
138 0 : for(i=0;i<4;i++){
139 : //std::cout << "--------------------------------------------------" << std::endl;
140 0 : Matrix[i/2][i%2] = EvtLeptonSCurrent(parent->sp(i/2),parent->getDaug(0)->spParent(i%2));
141 : //std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
142 0 : Matrix[i/2][i%2] -= m_B_to_A*EvtLeptonPCurrent(parent->sp(i/2),parent->getDaug(0)->spParent(i%2));
143 : //std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
144 : //Matrix[i/2][i%2] *= G_F*M_pi*M_pi;
145 : //std::cout << "Matrix = " << Matrix[i/2][i%2] << std::endl;
146 : //std::cout << "--------------------------------------------------" << std::endl;
147 0 : amp->vertex(i/2,i%2,Matrix[i/2][i%2]);
148 : }
149 :
150 0 : if(m_noTries>0) if(!((++noTries)%m_noTries)) report(Severity::Debug,"EvtGen") << " EvtHypNonLepton already finished " << noTries << " matrix element calculations" << std::endl;
151 0 : }
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