FlightTimeEstimator.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/trackingUtilities/numerics/LookupTable.h>
#include <tracking/trackingUtilities/geometry/VectorUtil.h>
 
#include <Math/Vector2D.h>
#include <Math/VectorUtil.h>
 
#include <memory>
#include <cmath>
 
namespace Belle2 {
  namespace TrackFindingCDC {

    class FlightTimeEstimator {
 
    public:
      virtual ~FlightTimeEstimator() = default;

      virtual double
      getFlightTime2D(const ROOT::Math::XYVector& /*pos2D*/, double /*alpha*/, double /*beta */ = 1) const
      {
        return 0;
      }
 
    public:
      static const FlightTimeEstimator&
      instance(std::unique_ptr<FlightTimeEstimator> replacement = nullptr);
    };

    class BeamEventFlightTimeEstimator : public FlightTimeEstimator {
 
    public:
      BeamEventFlightTimeEstimator();

      double getFlightTime2D(const ROOT::Math::XYVector& pos2D, double alpha, double beta = 1) const override
      {
        double absAlpha = std::fabs(alpha);
        double directDist2D = pos2D.R();
        return directDist2D * m_firstPeriodAlphaFlightTimeFactor(absAlpha) / beta;
      }
 
    private:
      TrackingUtilities::LookupTable<float> m_firstPeriodAlphaFlightTimeFactor;
    };

    class CosmicRayFlightTimeEstimator : public FlightTimeEstimator {
 
    public:
      explicit CosmicRayFlightTimeEstimator(ROOT::Math::XYZVector triggerPoint = ROOT::Math::XYZVector(0, 0, 0));

      double getFlightTime2D(const ROOT::Math::XYVector& pos2D, double alpha, double beta = 1) const override
      {
        ROOT::Math::XYVector relPos2D = pos2D - VectorUtil::getXYVector(m_triggerPoint);
        double deltaAlpha = ROOT::Math::VectorUtil::DeltaPhi(pos2D, relPos2D);
        alpha += deltaAlpha;
        double absAlpha = std::fabs(alpha);
        double directDist2D = relPos2D.R();
        return directDist2D * m_halfPeriodAlphaFlightTimeFactor(absAlpha) / beta;
      }
 
    private:
      TrackingUtilities::LookupTable<float> m_halfPeriodAlphaFlightTimeFactor;

      ROOT::Math::XYZVector m_triggerPoint;
    };
 
  }
}