TransportedSMParticle.cxx

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#include "AtlfastEvent/TransportedSMParticle.h"
#include "AtlfastEvent/ChargeService.h"
#include "AtlfastEvent/MagField.h"

#include <iostream>
#include <cmath>

namespace Atlfast {

  // std::abs accepts doubles and floats
  using std::abs;
  using std::cout;
  using std::flush;
  using std::endl;

  void TransportedSMParticle::deflect(){

    // A Phi object is held as a member
    double phi=m_phi.val();
  
    // Use ChargeService to get particle's charge
    double charge;
    ChargeService cs;
    try{
      charge=cs(m_particle);
    }catch(std::string errMsg){
      throw errMsg;
    }
    
    
    MagField *bfield = MagField::Instance();
    
    if( bfield->is_on() && !(charge==0.) ) {
      
      //cout << "deflect phi: " << phi << flush;

      assert(std::abs(charge)>0.5);
      
      double def=0.;
      double theta = m_particle->momentum().theta();
      double eta = m_particle->momentum().eta();
      double pt = m_particle->momentum().perp();
      

      if (abs(eta) < 1.4) {

        // Conversion factor of 3.0: 
        //     3e8 (from c in MeV/c, for pT) /
        //     100 (calorimeter radius measured in cm) /
        //     1e6 (from MeV in MeV/c, for pT)
        // Don't understand the factor of 2.0 at end of expression

        def = -150. * bfield->strength() * 3.0 / ( pt * 2.0 );
      } else { 
        def = -350.*abs(tan(theta)) * bfield->strength() * 3.0 / ( pt * 2.0 );
      }
      
      if(double turns =(def/(2*M_PI))>5.0) {
        cout<<"MagField: particle has spun  "<<turns<<" pt= "<<pt<<endl;
      } 
      
      // Replace member Phi with deflected version
      m_phi = phi + def*charge;
      
      //cout << " ==> " << m_phi.val() << endl;
      
    }
    
    return;
    
  }
  
}

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