Reconstruction/MdcPatRec/TrkBase/include/TrkBase/TrkMomCalculator.h

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//--------------------------------------------------------------------------
// File and Version Information:
//
// Description:  TrkMomCalculator is the momentum calculation engine
//      for the TrkMomVisitor implementation of the Visitor pattern,
//      for use in calculating momenta for different types of
//      trajectories.  Important note: in calculating momentum, these
//      functions make assumptions about how trajectories relate to mom.
//      Specifically, they assume: 1) that mom should be calculated using
//      the nominal B field, not B at the point in question -- this is valid
//      for (today's) KalmanTrack, but is not true in general; 2) that
//      B is parallel to the z axis.
//
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Author(s): Justin Albert, Steve Schaffner
//
//------------------------------------------------------------------------
 
#ifndef TRKMOMCALCULATOR_HH
#define TRKMOMCALCULATOR_HH
#include "CLHEP/Matrix/Matrix.h"
#include "CLHEP/Matrix/SymMatrix.h"
#include "CLHEP/Vector/ThreeVector.h"
 
class TrkSimpTraj;
namespace MdcPatRec {
  class BField;
}
 
using CLHEP::Hep3Vector;
using CLHEP::HepMatrix;
using CLHEP::HepSymMatrix;
using CLHEP::HepVector;
class BesVectorErr;
 
// Class interface //
class TrkMomCalculator {
 
public:
  TrkMomCalculator();
  virtual ~TrkMomCalculator();
 
  //********************************
  // The calculator functions:
  //********************************
 
  static double       ptMom( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen );
  static Hep3Vector   vecMom( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen );
  static BesVectorErr errMom( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen );
  static int          charge( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen );
 
  // Interface to vertexing algorithms (M.Bondioli 7/17/98)
  // covariance matrices of the track at fixed flight length
  static HepMatrix posmomCov( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen );
  static void      getAllCovs( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                               HepSymMatrix& xxCov, HepSymMatrix& ppCov, HepMatrix& xpCov );
  // invert 6x6
  static bool weightToCov( const HepSymMatrix& inXX, const HepSymMatrix& inPP,
                           const HepMatrix& inXP, HepSymMatrix& outXX, HepSymMatrix& outPP,
                           HepMatrix& outXP );
 
  // accessors to 2nd derivative of chi2 wrt x and p.
  // x0 and p0 are filled with the pos and 3mom around which expansion
  // takes place, whilst Weights are filled with the 2nd deriv of chi2.
  // so that:
  //  dx=x-x0   dp=p-p0
  //
  //  chi2(x,p)=0.5 dx^t*Wxx*dx + dx^t*Wxp*dp + 0.5 dp^t*Wpp*dp
  // where:
  //  pos and mom are 3-dim Vectors,
  //  xxWeight ppWeight and xpWeight are 3 by 3 matrices
  //
  // takes place, whilst Weights are filled with the 2nd deriv of chi2.
  // so that:
  //  dx=x-x0   dp=p-p0
  //
  //  chi2(x,p)=0.5 dx^t*Wxx*dx + dx^t*Wxp*dp + 0.5 dp^t*Wpp*dp
  // where:
  //  pos and mom are 3-dim Vectors,
  //  xxWeight ppWeight and xpWeight are 3 by 3 matrices
  //
  static void getAllWeights( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                             HepVector& pos, HepVector& mom, HepSymMatrix& xxWeight,
                             HepSymMatrix& ppWeight, HepMatrix& xpWeight );
 
private:
  static double calcCurvPtMom( const Hep3Vector&, double curvature, const MdcPatRec::BField& );
  static Hep3Vector   calcCurvVecMom( const Hep3Vector&, double curvature,
                                      const MdcPatRec::BField& );
  static BesVectorErr calcCurvErrMom( const TrkSimpTraj&, const MdcPatRec::BField&,
                                      double flt );
  static BesVectorErr calcNeutErrMom( const TrkSimpTraj&, const MdcPatRec::BField&,
                                      double flt );
  static int calcCurvCharge( const Hep3Vector&, double curvature, const MdcPatRec::BField& );
 
  static HepMatrix calcCurvPosmomCov( const TrkSimpTraj&, const MdcPatRec::BField&,
                                      double fltlen );
  static HepMatrix calcNeutPosmomCov( const TrkSimpTraj&, const MdcPatRec::BField&,
                                      double fltlen );
 
  static void calcCurvAllCovs( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                               HepSymMatrix& xxCov, HepSymMatrix& ppCov, HepMatrix& xpCov );
 
  static void calcCurvAllCovsOLD( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                                  HepSymMatrix& xxCov, HepSymMatrix& ppCov, HepMatrix& xpCov );
 
  static void calcNeutAllCovs( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                               HepSymMatrix& xxCov, HepSymMatrix& ppCov, HepMatrix& xpCov );
 
  static void calcNeutAllCovs( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                               HepVector& x0, HepVector& p0, HepSymMatrix& xxCov,
                               HepSymMatrix& ppCov, HepMatrix& xpCov );
 
  static void calcCurvAllWeights( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                                  HepVector& pos, HepVector& mom, HepSymMatrix& xxWeight,
                                  HepSymMatrix& ppWeight, HepMatrix& xpWeight );
 
  static void calcCurvAllWeightsOLD( const TrkSimpTraj&, const MdcPatRec::BField&,
                                     double fltlen, HepVector& pos, HepVector& mom,
                                     HepSymMatrix& xxWeight, HepSymMatrix& ppWeight,
                                     HepMatrix& xpWeight );
 
  static void calcNeutAllWeights( const TrkSimpTraj&, const MdcPatRec::BField&, double fltlen,
                                  HepVector& pos, HepVector& mom, HepSymMatrix& xxWeight,
                                  HepSymMatrix& ppWeight, HepMatrix& xpWeight );
 
  static int nearestInt( double );
};
 
#endif