SlopeRZ.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
 
#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;
    }
  };
 
}