PCmsLabTransform.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 <mdst/dbobjects/CollisionBoostVector.h>
#include <mdst/dbobjects/CollisionInvariantMass.h>
#include <mdst/dbobjects/CollisionAxisCMS.h>
#include <framework/database/DBObjPtr.h>
#include <framework/geometry/B2Vector3.h>
 
#include <Math/Boost.h>
#include <Math/AxisAngle.h>
#include <Math/LorentzRotation.h>
#include <Math/Vector4D.h>
 
namespace Belle2 {
  class PCmsLabTransform {
 
  public:
 
    PCmsLabTransform();
 
    B2Vector3D getBoostVector() const
    {
      return m_boostVectorDB->getBoost();
    }
 
    double getCMSEnergy() const
    {
      return m_invariantMassDB->getMass();
    }
 
    ROOT::Math::PxPyPzEVector getBeamFourMomentum() const
    {
      return rotateCmsToLab() * ROOT::Math::PxPyPzEVector(0, 0, 0, getCMSEnergy());
    }
 
    const ROOT::Math::LorentzRotation rotateLabToCms() const
    {
      //boost to CM frame
      ROOT::Math::LorentzRotation boost(ROOT::Math::Boost(-1.*getBoostVector()));
 
 
      //rotation such that the collision axis is aligned with z-axis
      ROOT::Math::XYZVector zaxis(0., 0., 1.); //target collision axis
 
      double tanAngleXZ = tan(m_axisCmsDB->getAngleXZ());
      double tanAngleYZ = tan(m_axisCmsDB->getAngleYZ());
      double Norm   = 1 / sqrt(1 + pow(tanAngleXZ, 2) + pow(tanAngleYZ, 2));
      ROOT::Math::XYZVector electronCMS(Norm * tanAngleXZ, Norm * tanAngleYZ, Norm); //current collision axis
 
      ROOT::Math::XYZVector rotAxis = zaxis.Cross(electronCMS);
      double rotangle = asin(rotAxis.R());
 
      ROOT::Math::LorentzRotation rotation(ROOT::Math::AxisAngle(rotAxis, -rotangle));
 
 
      ROOT::Math::LorentzRotation trans = rotation * boost;
      return trans;
    }
 
    const ROOT::Math::LorentzRotation rotateCmsToLab() const
    {
      return rotateLabToCms().Inverse();
    }
 
    static ROOT::Math::PxPyPzMVector labToCms(const ROOT::Math::PxPyPzMVector& vec);
 
    static ROOT::Math::PxPyPzMVector cmsToLab(const ROOT::Math::PxPyPzMVector& vec);
 
    static ROOT::Math::PxPyPzEVector labToCms(const ROOT::Math::PxPyPzEVector& vec);
 
    static ROOT::Math::PxPyPzEVector cmsToLab(const ROOT::Math::PxPyPzEVector& vec);
 
  private:
    const DBObjPtr<CollisionInvariantMass> m_invariantMassDB; 
    const DBObjPtr<CollisionBoostVector> m_boostVectorDB; 
    const DBObjPtr<CollisionAxisCMS> m_axisCmsDB; 
  };
 
} // Belle2 namespace