EnhanceMPI.cxx

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#include "UserHooksUtils.h"
#include "UserSetting.h"
#include "Pythia8_i/UserHooksFactory.h"
#include <stdexcept>
#include <iostream>
 
namespace Pythia8{
  class EnhanceMPI;
}
 
Pythia8_UserHooks::UserHooksFactory::Creator<Pythia8::EnhanceMPI> EnhanceMPICreator("EnhanceMPI");
 
namespace Pythia8{
 
  class EnhanceMPI : public UserHooks{
    
  public:
    
    EnhanceMPI(): m_pTCut("EnhanceMPI:PTCut", 10.), m_nMPIVeto(3){
      
      std::cout<<"**********************************************************"<<std::endl;
      std::cout<<"*                                                        *"<<std::endl;
      std::cout<<"*        Enhancing MPI emissions with UserHook!          *"<<std::endl;
      std::cout<<"*                                                        *"<<std::endl;
      std::cout<<"**********************************************************"<<std::endl;
      
      m_passedEvent = 0;      
    }
    
    ~EnhanceMPI(){}
    
    bool doVetoMPIStep(int nMPI, const Event &event){
      
      // MPI 1 is the hard process.  We do not veto that!
      if(nMPI < 2){
        m_passedEvent = false;
        return false;
      }
      
      if(m_passedEvent) return false;
      
      // start at the end of the event record and work back
      // This is prior to showering, so there should be at most 2 new MPI emissions
      // event[0] is documentation, so stop before that.
      size_t nEmissions=0;
      for(int ii=event.size()-1; ii > 0 && nEmissions != 2; --ii){
        if(event[ii].status() != 33) continue;
        if(event[ii].pT() > m_pTCut(settingsPtr)){
          m_passedEvent = true;
          return false;
        }
        
        ++nEmissions;
      }
      
      if(nMPI == m_nMPIVeto && !m_passedEvent){
        //        std::cout<<"Vetoing event on too-little MPI"<<std::endl;
        return true;
      }
      
      return false;
    }
    
    bool doVetoPartonLevel(const Event&){
      if(m_passedEvent) return false;
      
      return true;
    }
    
    bool canVetoMPIStep(){return true;}
    int numberVetoMPIStep(){return m_nMPIVeto;}
    bool canVetoISREmission(){return false;}
    bool canVetoFSREmission(){return false;}
    bool canVetoPartonLevel(){return true;}
    
  private:
    
    Pythia8_UserHooks::UserSetting<double> m_pTCut;
    
    bool m_passedEvent;
    
    int m_nMPIVeto;
         
  };
  
  
 
}