VXDMomentumEstimation.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/vxdMomentumEstimation/VXDMomentumEstimationTools.h>
 
 
namespace Belle2 {
  template <class ClusterType>
  class VXDMomentumEstimation {
 
  private:
    VXDMomentumEstimation() { }
    VXDMomentumEstimation(const VXDMomentumEstimation&);
    VXDMomentumEstimation& operator = (const VXDMomentumEstimation&);
 
  public:
    struct FitParameters {
      double aE = 1.56173140e+07;
      double bE = -9.89192780e+03;
      double cE = 2.42177970e-02;
      double dE = 2.65702553e-08;
    };

    struct CorrectionFitParameters {
      double aM = 0;
      double bM = 0;
      double cM = 0;
      double dM = 0;
    };

    static const VXDMomentumEstimation& getInstance()
    {
      static VXDMomentumEstimation instance;
      return instance;
    }

    static double estimateQOverP(const ClusterType& cluster, const ROOT::Math::XYZVector& momentum,
                                 const ROOT::Math::XYZVector& position,
                                 short charge,
                                 const FitParameters& fitParameters, const CorrectionFitParameters& correctionFitParameters)
    {
      const VXDMomentumEstimationTools<ClusterType>& tools = VXDMomentumEstimationTools<ClusterType>::getInstance();
 
      const double dEdX = tools.getDEDX(cluster, momentum, position, charge);
      const double momentumEstimation = convertDEDXToMomentum(dEdX, fitParameters, correctionFitParameters);
      const double QOverP = charge / momentumEstimation;
 
      return QOverP;
    }

    static double estimateQOverPWithThickness(const ClusterType& cluster, short charge, const FitParameters& fitParameters,
                                              const CorrectionFitParameters& correctionFitParameters)
    {
      const VXDMomentumEstimationTools<ClusterType>& tools = VXDMomentumEstimationTools<ClusterType>::getInstance();
 
      const double dEdX = tools.getDEDXWithThickness(cluster);
      const double momentumEstimation = convertDEDXToMomentum(dEdX, fitParameters, correctionFitParameters);
      const double QOverP = charge / momentumEstimation;
 
      return QOverP;
    }

    static double convertDEDXToMomentum(double dEdX, const FitParameters& fitParameters,
                                        const CorrectionFitParameters& correctionFitParameters)
    {
      const double firstPart = fitParameters.aE / (dEdX - fitParameters.bE) / (dEdX - fitParameters.bE);
      const double lastPart = fitParameters.cE + fitParameters.dE * dEdX;
      const double estimation = firstPart + lastPart;
 
      const double quadPart = correctionFitParameters.aM * estimation * estimation;
      const double linearPart = correctionFitParameters.bM * estimation;
      const double constantPart = correctionFitParameters.cM;
      const double cubicPart = correctionFitParameters.dM * estimation * estimation * estimation;
      const double mediumCorrection = cubicPart + quadPart + linearPart + constantPart;
 
      const double estimationWithMediumCalibration = estimation - mediumCorrection;
      return estimationWithMediumCalibration;
    }
 
  };

}