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 // Jim Hunt June 4, 2008 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_WEIGHTED.hh"
34 EvtVVPIPI_WEIGHTED::~EvtVVPIPI_WEIGHTED() {}
36 std::string EvtVVPIPI_WEIGHTED::getName(){
38 return "VVPIPI_WEIGHTED";
43 EvtDecayBase* EvtVVPIPI_WEIGHTED::clone(){
45 return new EvtVVPIPI_WEIGHTED;
49 void EvtVVPIPI_WEIGHTED::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_WEIGHTED 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_WEIGHTED::initProbMax() {
76 //Hard coded... should not be hard to calculate...
77 setProbMax(0.08* 1.13 );
80 double reweight_event(double pipi_mass)
85 0.019119831948029617 * pipi_mass +
86 -1.8962883732377376e-05 * pipi_mass * pipi_mass
90 void EvtVVPIPI_WEIGHTED::decay( EvtParticle *psi_prime){
92 psi_prime->initializePhaseSpace(getNDaug(),getDaugs());
94 EvtParticle *jpsi,*pi1,*pi2;
96 jpsi=psi_prime->getDaug(0);
97 pi1=psi_prime->getDaug(1);
98 pi2=psi_prime->getDaug(2);
100 // Put phase space results into the daughters.
102 EvtVector4C ep0,ep1,ep2;
104 ep0=psi_prime->eps(0);
105 ep1=psi_prime->eps(1);
106 ep2=psi_prime->eps(2);
108 EvtVector4C e0,e1,e2;
110 e0 = jpsi->epsParent(0);
111 e1 = jpsi->epsParent(1);
112 e2 = jpsi->epsParent(2);
114 double mass2 = (pi1->getP4()+pi2->getP4()).mass2();
116 double fac = mass2-4*pi1->mass()*pi2->mass();
118 fac *= reweight_event(sqrt(mass2));
120 vertex(0,0,fac*(ep0*e0.conj()));
121 vertex(0,1,fac*(ep0*e1.conj()));
122 vertex(0,2,fac*(ep0*e2.conj()));
124 vertex(1,0,fac*(ep1*e0.conj()));
125 vertex(1,1,fac*(ep1*e1.conj()));
126 vertex(1,2,fac*(ep1*e2.conj()));
128 vertex(2,0,fac*(ep2*e0.conj()));
129 vertex(2,1,fac*(ep2*e1.conj()));
130 vertex(2,2,fac*(ep2*e2.conj()));