1 //--------------------------------------------------------------------------
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.
8 // Copyright Information: See EvtGen/COPYRIGHT
9 // Copyright (C) 1998 Caltech, UCSB
11 // Module: EvtVVSPwave.cc
13 // Description: Routine to decay vector-> vector pi pi where the
14 // decay is S-wave dominated.
16 // Modification history:
18 // RYD December 11, 1999 Module created
20 //------------------------------------------------------------------------
22 #include "EvtGenBase/EvtPatches.hh"
24 #include "EvtGenBase/EvtParticle.hh"
25 #include "EvtGenBase/EvtGenKine.hh"
26 #include "EvtGenBase/EvtPDL.hh"
27 #include "EvtGenBase/EvtVector4C.hh"
28 #include "EvtGenBase/EvtTensor4C.hh"
29 #include "EvtGenBase/EvtReport.hh"
30 #include "EvtGenModels/EvtVVpipi.hh"
34 EvtVVpipi::~EvtVVpipi() {}
36 std::string EvtVVpipi::getName(){
43 EvtDecayBase* EvtVVpipi::clone(){
49 void EvtVVpipi::init(){
51 static EvtId PIP=EvtPDL::getId("pi+");
52 static EvtId PIM=EvtPDL::getId("pi-");
53 static EvtId PI0=EvtPDL::getId("pi0");
55 // check that there are 0 arguments
59 checkSpinParent(EvtSpinType::VECTOR);
60 checkSpinDaughter(0,EvtSpinType::VECTOR);
64 if ((!(getDaug(1)==PIP&&getDaug(2)==PIM))&&
65 (!(getDaug(1)==PI0&&getDaug(2)==PI0))) {
66 report(ERROR,"EvtGen") << "EvtVVpipi generator expected "
67 << " pi+ and pi- (or pi0 and pi0) "
68 << "as 2nd and 3rd daughter. "<<endl;
69 report(ERROR,"EvtGen") << "Will terminate execution!"<<endl;
75 void EvtVVpipi::initProbMax() {
77 //Hard coded... should not be hard to calculate...
82 void EvtVVpipi::decay( EvtParticle *p){
84 p->initializePhaseSpace(getNDaug(),getDaugs());
86 EvtParticle *v,*s1,*s2;
92 // Put phase space results into the daughters.
94 EvtVector4C ep0,ep1,ep2;
100 double fac=(s1->getP4()+s2->getP4()).mass2()-4*s1->mass()*s2->mass();
102 vertex(0,0,fac*(ep0*v->epsParent(0).conj()));
103 vertex(0,1,fac*(ep0*v->epsParent(1).conj()));
104 vertex(0,2,fac*(ep0*v->epsParent(2).conj()));
106 vertex(1,0,fac*(ep1*v->epsParent(0).conj()));
107 vertex(1,1,fac*(ep1*v->epsParent(1).conj()));
108 vertex(1,2,fac*(ep1*v->epsParent(2).conj()));
110 vertex(2,0,fac*(ep2*v->epsParent(0).conj()));
111 vertex(2,1,fac*(ep2*v->epsParent(1).conj()));
112 vertex(2,2,fac*(ep2*v->epsParent(2).conj()));