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 "EvtPhspStepf.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtGlobalSet.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtRandom.hh"
#include "../EvtGenBase/EvtReport.hh"
#include <stdlib.h>
#include <string>
 
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;
}