VKalAtlasMagFld.cxx

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/*
  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
*/
 
//  AtlasMagFld object inherits from Trk::baseMagFld.  So pointer
//  AtlasMagFld*  is transferred to VKalVrtCore through VKalVrtControlBase object
//  Then this field is used in CORE for fitting
//
//
//  MAGNETIC FIELD IS ALWAYS GIVEN AT GLOBAL REFERENCE FRAME !!!
//    ref.frame origin (state.m_refFrameX, state.m_refFrameY, state.m_refFrameZ) is always added to coordinates
//    supplied to getMagFld().
//    default of ref.frame origin is (0,0,0) but may be changed if input tracks have different frame.
//
//
//  ATHENA  object "m_fitField" of AtlasMagFld type is created in VKalVrtFitter during init.
//  By default it gives constant magnetic field value of which may be changed through
//  jobOption "baseMagneticField" during initialization.
//   Magnetic field at (0,0,0)
//       before 13.1.0   - 2.084 tesla
//       after  13.1.0   - 1.964 tesla
//       after  15.1.0   - 1.997 tesla
//
//  Currently works with both TrackingMagField and AtlasMagField
//
//-----------------------------------------------------------------------------------------------
 
// Header include
#include "TrkVKalVrtFitter/VKalAtlasMagFld.h"
#include "CLHEP/Units/SystemOfUnits.h"
//-------------------------------------------------
#include<iostream>
 
namespace Trk{
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//                  ATLAS magnetic field access
VKalAtlasMagFld::VKalAtlasMagFld()
    : m_magFrameX(0.), m_magFrameY(0.), m_magFrameZ(0.) {}
 
VKalAtlasMagFld::~VKalAtlasMagFld() = default;
//
//  Setting of parameters
//
void VKalAtlasMagFld::setAtlasField(MagField::AtlasFieldCache *pnt) {
  m_VKalAthenaField = pnt;
}
 
void VKalAtlasMagFld::setAtlasField(const double field) {
  m_FIXED_ATLAS_FIELD = field;
}
 
void VKalAtlasMagFld::setAtlasMagRefFrame(double x, double y, double z) {
  m_magFrameX = x;
  m_magFrameY = y;
  m_magFrameZ = z;
}
 
//
// Coordinates here are in mm. - default for TrkVKalVrtCore
//
void VKalAtlasMagFld::getMagFld(const double x, const double y, const double z,
                                double &bx, double &by, double &bz) {
  double fieldXYZ[3];
  double BField[3];
  fieldXYZ[0] = (x + m_magFrameX) * CLHEP::mm;
  fieldXYZ[1] = (y + m_magFrameY) * CLHEP::mm;
  fieldXYZ[2] = (z + m_magFrameZ) * CLHEP::mm;
  if (m_VKalAthenaField) {
    m_VKalAthenaField->getField(fieldXYZ, BField);
    bx = BField[0] / CLHEP::tesla;
    by = BField[1] / CLHEP::tesla;  // Field in TESLA!!!!
    bz = BField[2] / CLHEP::tesla;
  } else {
    bx = 0.;
    by = 0.;
    bz = m_FIXED_ATLAS_FIELD;
  }
}
}  // namespace Trk