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MagField.cxx

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//                                                                      //
// PS Magfield. Calculate bending due to Magnetic Field                 //
//                                                                      // 
//                                                                      //

#include "AtlfastAlgs/MagField.h" 
#include <cmath> 
#include "AtlfastEvent/Phi.h" 
namespace Atlfast{
  using std::abs;
  using std::cout;
  using std::endl;

  MagField::MagField(bool fieldOn): 
    m_fieldOn(fieldOn), m_chargeService(ChargeService()) {}

  void MagField::operator()( const MCparticleCollection& p, 
                             TransportedParticleCollection& atCal) const {
    
    // calculation of phi deflection due to B-field - from L. Poggioli
    MCparticleCollectionCIter ip= p.begin();
    for(; ip<p.end(); ++ip){
      double phi;
      phi=(*ip)->momentum().phi();
      double charge=m_chargeService(*ip);
      if(m_fieldOn && !(charge==0.) ) {
        
        double def=0.;
        double theta = (*ip)->momentum().theta();
        double eta = (*ip)->momentum().pseudoRapidity();
        double pt = (*ip)->momentum().perp();
        
        if (abs(eta) < 1.4) {def = -150. * 0.006/pt/2.0;}
        else { def = -350. * abs(tan(theta))* 0.006/pt/2.0;}
        
        if(double turns =(def/(2*M_PI))>5.0) {
          cout<<"MagField: particle has spun  "<<turns<<" pt= "<<pt<<endl;
        } 
        
        phi = Phi(phi + def*charge);
      }
      //      std::pair<double, HepMC::GenParticle*>* temp = 
      //new std::pair<double, HepMC::GenParticle*>(phi,*ip);
      //atCal.push_back( *temp );
      //delete temp;
      atCal.push_back( new TransportedParticle(phi, *ip));
    }
    
  }
}
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