TimePointBetaFitter.h

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/*
  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef MUON_STAU_TIMEPOINTBETAFITTER_H
#define MUON_STAU_TIMEPOINTBETAFITTER_H
 
#include <vector>
#include "GaudiKernel/PhysicalConstants.h"
 
static constexpr double const& invSpeedOfLight = 1 / Gaudi::Units::c_light; // need 1/299.792458
 
namespace Muon {
  
  class TimePointBetaFitter {
  public:
    struct Hit {
      Hit(float distance_, float time_, float error_ ) : distance(distance_), time(time_+distance*invSpeedOfLight), error(error_), useInFit(true), residual(0.) { weight2 = 1./(error*error); }

      float distance;  
      float time;      
      float error;     
      float weight2;   
      bool  useInFit;  
      float residual;  
    };
    typedef std::vector<Hit> HitVec; 

    struct FitResult {
      FitResult() : status(0), beta(0), chi2(0), ndof(1) {}
      FitResult(int status_, float beta_, float chi2_, int ndof_) : status(status_), beta(beta_), chi2(chi2_), ndof(ndof_) {}
      
      float chi2PerDOF() const { return (status == 0 || ndof == 0) ? 0 : chi2/ndof; }

      int status;  
      float beta;  
      float chi2;  
      int ndof;    
    };

    TimePointBetaFitter() {}

    static FitResult fit( HitVec& hits ) ;

    FitResult fitWithOutlierLogic( HitVec& hits ) const;
 
  };
 
}
 
#endif