MarlinTrackFit Class Reference

Public Member Functions
	MarlinTrackFit ()
	Constructor.
	~MarlinTrackFit ()
	Destructor.
int	DoFitting (int useExtraPoint, int fitOpt, int &nhits, float bField, int *idet, int *itype, float chi2PrefitCut, float *x, float *y, float *z, float *RPReso, float *ZReso, float *param, float *eparam, float *RefPoint, float &chi2, int &ndf, float &chi2rphi, float &chi2z, int *lhits)
	Method performs track fitting taking into account energy loss and MS First simple helix fit is performed to define initial track parameters at the PCA to primary IP. More...
void	CrudeErrorEstimates (float BField, float *reso, float *param, float *eparam)
	Method fills covariance matrix according to apriori specified resolutions Covariance matrix is assumed to be diagonal Inputs : reso[4] - array of resolutions : 0 - momentum resolution delta(Pt)/Pt^2 1 - angular resolution (radians) 2 - D0 resolution (mm) 3 - Z0 resolution (mm) param[5] - track parameters in the canonical representation Output : eparam[15] - covariance matrix
void	setParametersForIPErrors (float *par)

Member Function Documentation

int MarlinTrackFit::DoFitting	(	int	useExtraPoint,
		int	fitOpt,
		int &	nhits,
		float	bField,
		int *	idet,
		int *	itype,
		float	chi2PrefitCut,
		float *	x,
		float *	y,
		float *	z,
		float *	RPReso,
		float *	ZReso,
		float *	param,
		float *	eparam,
		float *	RefPoint,
		float &	chi2,
		int &	ndf,
		float &	chi2rphi,
		float &	chi2z,
		int *	lhits
	)

Method performs track fitting taking into account energy loss and MS First simple helix fit is performed to define initial track parameters at the PCA to primary IP.

If simple helix fit converges and has qood quality set by variable chi2PrefitCut then DELPHI fitting routine trkfit.F is envoked Inputs : useExtraPoint : 1 - an additional extra point (P.C.A) is used in fit with relatively large errors to improve D0 and Z0 determination @ P.C.A 0 - number of points in fit equals to the number of hits in track optFit : 0 - FORTRAN routine tfithl is used for prefit to determine initial track parameters 1 - ClusterShapes class is used for prefit nhits - number of tracker hits used in fit bField - magnetic field in Tesla idet - list of the hit detector identifiers itype - list of the hit types ( 2 - planar disks, 3 - cyllindrical or laddered detector ) chi2PrefitCut - cut on the chi2 of prefit. If chi2 of prefit > chi2 then prefit is regarded to fail and routine returns -1 x,y,z - list of the hit Cartesian coordinates RPReso - list of the hit resolutions in R-Phi projection ZReso - list of the hit resolutions along Z Outpus : param - list of the track parameters at the PCA param[0] - Omega (signed curvuture) sign "+" corresponds to clock-wise direction param[1] - tan(Lambda) (tangence of the dip angle, lambda = pi/2 - Theta) param[2] - Azimuthal angle of the particle momentum @ PCA param[3] - D0 (IP in the R-Phi projection @ PCA ) param[4] - Z0 (z coordinate displacement @ PCA ) eparam[15] - covariance matrix of the track parameters (lower-left part of symmetric matrix) RefPoint[3] - reference point of track fit chi2 - fit chi2 ndf - number of degrees of freedom chi2rphi - prefit chi2 in the R-Phi (X-Y) plane chi2z - prefit chi2 in the S-Z plane lhits - list of hit status after fit, lhits[i] = 0 means that hit is thrown away after fitting procedure lhits[i] = 1 means that hit is kept in the fitting procedure returned integer indicate error flag error = 0 - no error, fit is successfull error = -1 - simple helix fit failed error = 1 - Delphi fit failed, but the simple helix fit is successfull

Subroutine converts covariance matrix from the TANAGRA (DELPHI code) representation
(R-Phi,R-Phi)
(R-Phi,ZR) (ZR,ZR)
(R-Phi,Theta) (ZR,Theta) (Theta,Theta)
(R-Phi,PhiR) (ZR,PhiR) (Theta,PhiR) (PhiR,PhiR)
(R-Phi,1/p) (ZR,1/p) (Theta,1/p) (PhiR,1/p) (1/p,1/p)
into canonical representation
(D0,D0)
(Phi0,D0) (Phi0,Phi0)
(Omega,D0) (Omega,Phi0) (Omega,Omega)
(Z0,D0) (Z0,Phi0) (Z0,Omega) (Z0,Z0)
(TanL,D0) (TanL,Phi0) (TanL,Omega) (TanL,Z0) (TanL,TanL)

TANAGRA Vector Eta = (R-Phi,z,Theta,phi,1/p)
where R-Phi : R*Phi @ fixed Radius of the reference point
ZR : z coordinate of the reference point
Theta : polar angle of the momentum @ reference point
PhiR : azimuthal angle of the momentum @ reference point
1/p : inverse of momentum magnitude (signed quantity)
sign is "+" corresponds to anticlock-wise direction
as opposed to definition of Omega (in canonical format)
Canonical Vector X = (Omega,TanLambda,Phi,D0,Z0)

Covariance matrix is calculated according to
UX[i,j] = VEta[l,m]*dXdEta[i,l]*dXdEta[j,m]
where UX[i,j] is the cov matrix in the canonical representation
Veta[l,m] is the cov matrix in the TANAGRA (DELPHI) representation
and dXdEta[k,n] - is Jacobian dX_k/dEta_n

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The documentation for this class was generated from the following file:

• MarlinTrackFit.h