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: EvtGen/EvtVVpipiMoxhay.hh
13 // Description: This model is based on the proposal by Tuan and Lipkin
14 // (Phys.Lett.B206:349-353,1988) and the subsequent model
15 // by Moxhay (Phys.Rev.D39:3497,1989) for the dipion spectrum
16 // in Y(3S) -> pi+ pi- Y(1S). Please Note: in Moxhay's paper,
17 // he wrote the fitted value of the parameter Im(B)/A as
18 // -0.2983. However, using his quoted value leads to the wrong
19 // spectrum. Changing the sign of his quoted Im(B)/A fixes the
20 // shape and reproduces his result. Therefore, please pass
21 // Im(B)/A = 0.2983 and Re(B)/A = 0.2196 to get the correct shape
22 // based on his fit to the CLEO data.
27 // 1.0000 Upsilon pi+ pi- Y3STOY1SPIPIMOXHAY 0.2196 0.2983;
30 // --> the order of parameters is: Re(B)/A Im(B)/A
32 // Modification history:
34 // SEKULA November 02, 2007 Module created
36 //------------------------------------------------------------------------
39 #include "EvtGenBase/EvtPatches.hh"
41 #include "EvtGenBase/EvtParticle.hh"
42 #include "EvtGenBase/EvtGenKine.hh"
43 #include "EvtGenBase/EvtPDL.hh"
44 #include "EvtGenBase/EvtVector4C.hh"
45 #include "EvtGenBase/EvtTensor4C.hh"
46 #include "EvtGenBase/EvtReport.hh"
47 #include "EvtGenModels/EvtY3SToY1SpipiMoxhay.hh"
51 EvtY3SToY1SpipiMoxhay::~EvtY3SToY1SpipiMoxhay() {}
53 std::string EvtY3SToY1SpipiMoxhay::getName(){
55 return "Y3STOY1SPIPIMOXHAY";
60 EvtDecayBase* EvtY3SToY1SpipiMoxhay::clone(){
62 return new EvtY3SToY1SpipiMoxhay;
66 void EvtY3SToY1SpipiMoxhay::init(){
68 static EvtId PIP=EvtPDL::getId("pi+");
69 static EvtId PIM=EvtPDL::getId("pi-");
70 static EvtId PI0=EvtPDL::getId("pi0");
72 // check that there are 2 arguments
76 checkSpinParent(EvtSpinType::VECTOR);
77 checkSpinDaughter(0,EvtSpinType::VECTOR);
81 if ((!(getDaug(1)==PIP&&getDaug(2)==PIM))&&
82 (!(getDaug(1)==PI0&&getDaug(2)==PI0))) {
83 report(ERROR,"EvtGen") << "EvtY3SToY1SpipiMoxhay generator expected "
84 << " pi+ and pi- (or pi0 and pi0) "
85 << "as 2nd and 3rd daughter. "<<endl;
86 report(ERROR,"EvtGen") << "Will terminate execution!"<<endl;
92 void EvtY3SToY1SpipiMoxhay::initProbMax() {
96 void EvtY3SToY1SpipiMoxhay::decay( EvtParticle *p){
98 p->initializePhaseSpace(getNDaug(),getDaugs());
100 EvtParticle *v,*s1,*s2;
107 // setup the parameters needed for this model
109 double lambda = -0.73;
110 double m_sigma = 0.71;
112 double m_pi = s1->getP4().mass();
114 double MV1 = p->getP4().mass();
115 double MV2 = v->getP4().mass();
117 double q = (s1->getP4()+s2->getP4()).mass();
119 double EV2 = (MV1*MV1 - MV2*MV2 - q*q)/(2.0 * q);
121 double ReB_over_A = getArg(0);
122 double ImB_over_A = getArg(1);
127 Xi = EvtComplex( 2.0/EvtConst::pi * ( 1.0 - sqrt(1.0 - 4*m_pi*m_pi/(q*q)) * log( (sqrt(q*q) + sqrt(q*q-4.0*m_pi*m_pi))/(2*m_pi) )),
128 sqrt(1.0 - 4*m_pi*m_pi/(q*q)));
133 F = (g_spp*g_spp + lambda*(m_sigma*m_sigma - q*q)) / ( ( (m_sigma*m_sigma - q*q)*(1.0 - lambda*Xi) - (g_spp*g_spp*Xi) ) * 1.0/(8.0 * EvtConst::pi * f_pi*f_pi) * q * q );
136 B_over_A = EvtComplex(ReB_over_A, ImB_over_A);
138 // The dGamma/d(M_pipi) spectrum
141 dGdMpp = abs2((q*q*F - B_over_A)) * q * sqrt(q*q - 4 * m_pi *m_pi) * sqrt(EV2 * EV2 - MV2*MV2);
144 setProb( real(dGdMpp) );