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: EvtEtaDalitz.cc
13 // Description: Routine to decay eta -> pi+ pi- pi0
15 // Modification history:
17 // DJL/RYD July 23, 1997 Module created
19 //------------------------------------------------------------------------
21 #include "EvtGenBase/EvtPatches.hh"
23 #include "EvtGenBase/EvtParticle.hh"
24 #include "EvtGenBase/EvtGenKine.hh"
25 #include "EvtGenBase/EvtPDL.hh"
26 #include "EvtGenModels/EvtEtaDalitz.hh"
27 #include "EvtGenBase/EvtReport.hh"
30 EvtEtaDalitz::~EvtEtaDalitz() {}
32 std::string EvtEtaDalitz::getName(){
39 EvtDecayBase* EvtEtaDalitz::clone(){
41 return new EvtEtaDalitz;
45 void EvtEtaDalitz::init(){
47 // check that there are 0 arguments
51 checkSpinParent(EvtSpinType::SCALAR);
53 checkSpinDaughter(0,EvtSpinType::SCALAR);
54 checkSpinDaughter(1,EvtSpinType::SCALAR);
55 checkSpinDaughter(2,EvtSpinType::SCALAR);
59 void EvtEtaDalitz::initProbMax(){
65 void EvtEtaDalitz::decay( EvtParticle *p){
67 p->initializePhaseSpace(getNDaug(),getDaugs());
69 EvtVector4R mompi0 = p->getDaug(2)->getP4();
70 double masspip = p->getDaug(0)->mass();
71 double masspim = p->getDaug(1)->mass();
72 double masspi0 = p->getDaug(2)->mass();
73 double m_eta = p->mass();
77 //The decay amplitude coems from Layter et al PRD 7 2565 (1973).
79 y=(mompi0.get(0)-masspi0)*(3.0/(m_eta-masspip-masspim-masspi0))-1.0;
81 EvtComplex amp(sqrt(1.0-1.07*y),0.0);