SignCurvatureXYError.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 <framework/geometry/B2Vector3.h>
 
#include <math.h>
 
#define SIGNCURVATUREXYERROR_NAME SignCurvatureXYError
 
namespace Belle2 {
  template <typename PointType >
  class SIGNCURVATUREXYERROR_NAME : public SelectionVariable< PointType, 3, int > {
  public:
 
    PUT_NAME_FUNCTION(SIGNCURVATUREXYERROR_NAME);
 
    static int value(const PointType& a, const PointType& b, const PointType& c)
    {
      B2Vector3D sigma_a = a.getPositionError();
      B2Vector3D sigma_b = b.getPositionError();
      B2Vector3D sigma_c = c.getPositionError();
 
      B2Vector3D c2b(b.X() - c.X(), b.Y() - c.Y(), 0.0);
      B2Vector3D b2a(a.X() - b.X(), a.Y() - b.Y(), 0.0);
      //TODO: check if acos of the dot product is better (faster)
      double angle = atan2(b2a[0], b2a[1]) - atan2(c2b[0], c2b[1]);
      //TODO 1/3...mean of the sigmas. Possible improvement: Use a parameter instead, and determine with simulated events.
      double sigmaan = (sigma_a.Mag() + sigma_b.Mag() + sigma_c.Mag()) / (3.*(c2b.Mag() + b2a.Mag()));
      if (angle < (-sigmaan)) { return -1; }
      else if (angle > sigmaan)  {return 1; }
      else  { return 0; }
    }
 
  };
 
}