SimpleSmear.cc

#include "SimpleSmear.h"

#include "PythiaJetGun.hh"

namespace stab {

void SimpleSmear::smear(Event &smearEvent)  
{

  const unsigned nParts = m_event.size();
  smearEvent.resize(nParts);

  for ( unsigned i=0; i != nParts; i++ ) {
    const PseudoJet & part = m_event[i];
    const double m = part.m();

    const double mass = m==m ? m : 0.;
    const double p2 = part.modp2();
    const double etmp = sqrt(p2+mass*mass);

    const double eta = part.eta()+PythiaJetGun::gaussRandom(0.,m_sigmaEtaPhi);
    const double phi = part.phi()+PythiaJetGun::gaussRandom(0.,m_sigmaEtaPhi);
    double eShift = -1.;
    while ( eShift <= mass ) {
      eShift = etmp+PythiaJetGun::gaussRandom(0.,m_sigmaE);
    }
    const double e = eShift;
    
    const double mom =  e > mass ? sqrt(e*e-mass*mass) : 0.;
    const double pt = mom/cosh(eta);
    const double px = pt*cos(phi);
    const double py = pt*sin(phi);
    const double pz = pt*sinh(eta);

    smearEvent[i] = PseudoJet(px,py,pz,e);

  } 

}

}