EvtPhspStepf.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) 1998      Caltech, UCSB
//
// Module: EvtPhspStep.cc
//
// Description: Routine to decay a particle according th phase space, but with a stepfunction in a two-body subsystem
//
// Modification history:
//
//    RYD       January 8, 1997       Module created
//    N. Huesken      July 2022       model to suppress part of the phase-space in a multi-body decay
//    syntax in decay card (e.g.):
//    Decay J/psi
//    1.0 K+ K- pi+ pi- PhspStepf 0 1 1.0 1.04 0.9;
//    Enddecay
//    will generate J/psi --> K+K-pi+pi- in 4-body PHSP,
//    but with 90% of K+K- invariant masses outside the region 1.00-1.04 being vetoed during event generation
//    this allows for more efficient event generation for PWA with narrow resonances 
//
//    apart from the suppression, this is a copy of the PHSP model
//
//------------------------------------------------------------------------
//
#include "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenModels/EvtPhspStepf.hh"
#include "EvtGenModels/EvtGlobalSet.hh"
#include <string>
#include "EvtGenBase/EvtRandom.hh"
#include "EvtGenBase/EvtPDL.hh"
 
EvtPhspStepf::~EvtPhspStepf() {}
 
void EvtPhspStepf::getName(std::string& model_name){
 
  model_name="PhspStepf";     
 
}
 
EvtDecayBase* EvtPhspStepf::clone(){
 
  return new EvtPhspStepf;
 
}
 
 
void EvtPhspStepf::init(){
  // check that there are 5 arguments
  checkNArg(5);
  idx1 = (int)getArg(0);
  idx2 = (int)getArg(1);
  //  std::cout << idx1 << " " << idx2 << std::endl;
  mass_min = getArg(2);
  mass_max = getArg(3);
  frac = getArg(4);
}
 
void EvtPhspStepf::initProbMax(){
 
  noProbMax();
 
}
 
void EvtPhspStepf::decay( EvtParticle *p ){
 
  //unneeded - lange - may13-02
  //if ( p->getNDaug() != 0 ) {
    //Will end up here because maxrate multiplies by 1.2
  //  report(DEBUG,"EvtGen") << "In EvtPhspStep: has "
  //               <<" daugthers should not be here!"<<endl;
  //  return;
  //}  
 EvtFilter:
  double weight = p->initializePhaseSpace(getNDaug(),getDaugs());
  //  std::cout<<"weight= "<<weight<<std::endl;
  //  std::cout << idx1 << " " << idx2 << std::endl;
  if(((p->getDaug(idx1)->getP4()+p->getDaug(idx2)->getP4()).mass() < mass_min || (p->getDaug(idx1)->getP4()+p->getDaug(idx2)->getP4()).mass() > mass_max) && EvtRandom::Flat(0.0, 1.0)<frac){
    goto EvtFilter;
  }
 
  if(!EvtGlobalSet::iVV.size()) return;
 
  for(int i=0;i<EvtGlobalSet::iVV.size();i++){
    EvtVector4R psum(0,0,0,0);
    for(int j=0;j<EvtGlobalSet::iVV[i].size();j++){
      int idx =EvtGlobalSet::iVV[i][j]; 
      psum += p->getDaug(idx)->getP4(); 
      //debugging
      //std::cout<<idx<<std::endl;
    }
    double xmass=psum.mass();
    //std::cout<<xmass<<" "<<EvtGlobalSet::dVV[i][0]<<" "<<EvtGlobalSet::dVV[i][1]<<std::endl;
    if(xmass<EvtGlobalSet::dVV[i][0] || xmass>EvtGlobalSet::dVV[i][1]) goto EvtFilter;
  }  
  return ;
}