EvtSVSCPLH.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 2001      Caltech, UCSB
//
// Module: EvtSVSCPLH.cc
//
// Description: The decay of a scalar to a scalar and a vector particle are 
//              performed with CP violation and different widths for
//              the cp even and odd states. E.g. B->J/psi K_S.
//
// Modification history:
//
//    Ryd       March 29, 2001       Module created
//
//------------------------------------------------------------------------
//
#include "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtCPUtil.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenModels/EvtSVSCPLH.hh"
#include "EvtGenBase/EvtId.hh"
#include <string>
#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtVector4C.hh"
using std::endl;
 
EvtSVSCPLH::~EvtSVSCPLH() {}
 
void EvtSVSCPLH::getName(std::string& model_name){
 
  model_name="SVS_CPLH";     
 
}
 
 
EvtDecayBase* EvtSVSCPLH::clone(){
 
  return new EvtSVSCPLH;
 
}
 
void EvtSVSCPLH::init(){
 
  // check that there are 8 arguments
  checkNArg(8);
  checkNDaug(2);
 
  checkSpinParent(EvtSpinType::SCALAR);
 
  checkSpinDaughter(0,EvtSpinType::VECTOR);
  checkSpinDaughter(1,EvtSpinType::SCALAR);
 
  static double ctau=EvtPDL::getctau(EvtPDL::getId("B0"));
 
  // hbar/s
  _dm=getArg(0);
  _dgamma=EvtConst::c*getArg(1)/ctau;
 
  _qop=getArg(2)*exp(EvtComplex(0.0,getArg(3)));
 
  _poq=1.0/_qop;
 
  _Af=getArg(4)*exp(EvtComplex(0.0,getArg(5)));
  _Abarf=getArg(6)*exp(EvtComplex(0.0,getArg(7)));
  
  if (verbose()){
    report(INFO,"EvtGen")<<":EvtSVSCPLH:dm="<<_dm<<endl;
    report(INFO,"EvtGen")<<":EvtSVSCPLH:dGamma="<<_dgamma<<endl;
    report(INFO,"EvtGen")<<":EvtSVSCPLH:q/p="<<_qop<<endl;
    report(INFO,"EvtGen")<<":EvtSVSCPLH:Af="<<_Af<<endl;
    report(INFO,"EvtGen")<<":EvtSVSCPLH:Abarf="<<_Abarf<<endl;
  }
 
 
}
 
void EvtSVSCPLH::initProbMax(){
 
  //This is probably not quite right, but it should do as a start...
  //Anders
 
  setProbMax(4.0*(getArg(4)*getArg(4)+getArg(6)*getArg(6)));
 
}
 
void EvtSVSCPLH::decay( EvtParticle *p){
 
  p->initializePhaseSpace(getNDaug(),getDaugs());
 
  static EvtId B0=EvtPDL::getId("B0");
  static EvtId B0B=EvtPDL::getId("anti-B0");
 
  double t;
  EvtId other_b;
 
  EvtCPUtil::OtherB(p,t,other_b,0.5);
 
  //convert time from mm to seconds
  t/=EvtConst::c;
 
  //sign convention is dm=Mheavy-Mlight
  //                   dGamma=Gammalight-Gammaheavy
  //such that in the standard model both of these are positive.
  EvtComplex gp=0.5*(exp(EvtComplex(0.25*t*_dgamma,-0.5*t*_dm))+exp(EvtComplex(-0.25*t*_dgamma,0.5*t*_dm)));
  EvtComplex gm=0.5*(exp(EvtComplex(0.25*t*_dgamma,-0.5*t*_dm))-exp(EvtComplex(-0.25*t*_dgamma,0.5*t*_dm)));
 
  EvtComplex amp;
 
  if (other_b==B0B){
    amp=gp*_Af+_qop*gm*_Abarf;
  }
  else if (other_b==B0){
    amp=gp*_Abarf+_poq*gm*_Af;
  }
  else{
    report(ERROR,"EvtGen") << "other_b was not B0 or B0B!"<<endl;
    ::abort();
  }
 
  EvtVector4R p4_parent=p->getP4Restframe();;
  
  double norm=p->getDaug(0)->mass()/(p->getDaug(0)->getP4().d3mag()*p4_parent.mass());
 
  EvtParticle* v=p->getDaug(0);
 
  vertex(0,amp*norm*(p4_parent*(v->epsParent(0))));
  vertex(1,amp*norm*(p4_parent*(v->epsParent(1))));
  vertex(2,amp*norm*(p4_parent*(v->epsParent(2))));
  
 
  return ;
}