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SmearHardPhoton.cxx

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#include "FastShowerUtils/Normalisers/SmearHardPhoton.h"

#include "FastShowerUtils/ParticleParameters.h"

#include "FastShowerUtils/ProcessedNormal.h"
#include "CLHEP/Random/RandFlat.h"

#include <float.h>
#include <cmath>

namespace FastShower{

  double SmearHardPhoton::value(const ParticleParameters& pp) const{
  
    double energy = pp.rawEnergy();
    double aEta = fabs(pp.eta());

    energy = max((float)energy,FLT_EPSILON);

    double pt = energy*std::sin(2*std::atan(std::exp(aEta)));
    double sigmaSquared = 0.01/energy;
    if (aEta<1.4){
      sigmaSquared = sigmaSquared + 0.060025/pt/pt;
    }else{
      sigmaSquared = sigmaSquared 
                    +  std::pow((0.306*((2.4-aEta)+0.228)/energy),2);
    }
    sigmaSquared = sigmaSquared + 0.000049;
    
    double sigma;
    ProcessedNormal normal;
    do {sigma = normal.sample()*std::sqrt(sigmaSquared);}
     while (sigma<-1.0);
    
    return  1.0 + sigma;
  }
  //
  IFnOfParticleParameters* SmearHardPhoton::clone() const {
    return new SmearHardPhoton(*this);
  }
}//namespace

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