SlopeRZ.h

/**************************************************************************
* BASF2 (Belle Analysis Framework 2)                                     *
* Copyright(C) 2014 - Belle II Collaboration                             *
*                                                                        *
* Author: The Belle II Collaboration                                     *
* Contributors: Jakob Lettenbichler (jakob.lettenbichler@oeaw.ac.at)     *
*                                                                        *
* This software is provided "as is" without any warranty.                *
**************************************************************************/
 
#pragma once
 
#include <tracking/trackFindingVXD/filterMap/filterFramework/SelectionVariable.h>
#include <cmath>
 
#define SLOPERZ_NAME SlopeRZ
 
namespace Belle2 {
  template <typename PointType >
  class SLOPERZ_NAME : public SelectionVariable< PointType , 2 , double > {
  public:
    PUT_NAME_FUNCTION(SLOPERZ_NAME);
 
 
    static double value(const PointType& outerHit, const PointType& innerHit)
    {
      double result = atan(
                        sqrt(std::pow(double(outerHit.X() - innerHit.X()), 2)
                             + std::pow(double(outerHit.Y() - innerHit.Y()), 2)
                            ) / double(outerHit.Z() - innerHit.Z())
                      );
      // atan also returns negative angles, so map back to [0,Pi] otherwise one get two peaks at +/-Pi/2 for 90 degree angles
      if (result < 0.0) result += M_PI;
 
      // TODO: check if 0 is a good default return value in the case z_i==z_o!
      return (std::isnan(result) || std::isinf(result)) ? double(0) : result;
    }
  };
 
}