4.6.6 SUBROUTINE ZAUIMP(PAR, WGT, XYZ, VCOV, THJET, PHIJET, SIGNTP, IPRF, IPZ, EIPRF, EIPZ, CORREL) : IMPact parameter

This routine calculates the life-time signed impact-parameters in R-phi and z of a track w.r.t. a specified vertex.

The impact parameter in RF is the point of closest approach in the xy projection between the track and the vertex. The impact parameter in z is the z coordinate (after subtracting the z of the vertex) on the track helix at the point of closest approach in the xy plane. Life time signing means that the sign is positive if the track crosses the jet-axis after the perigee (going along the track in the direction of the momentum), the xy projection and the z projection independently. (The z-projection plane is the plane that contains the track tangent at the xy-perigee and that is parallel to the z axis). Geometric signing in RF means that the sigh is positive if the vertex is to the right when one stands at the perigee, looking along the track in the direction of its momentum and with ones head in the direction of the z-axis. In z, it is simply the sign of the z coordinate (z of the vertex subtracted).

ARGUMENTS:

INPUT :

    PAR & WGT : TKR parameters with weight matrix at the perigee
                 for the track
            fit
    XYZ & VCOV : position and cov-matrix of primary vertex
    THJET & PHIJET : Theta and Phi of the jet axis (ignored if SIGNTP <>
             'LIFE'.
    SIGNTP : 'LIFE' -> life-time sign; any other value -> geometric
             signing.

OUTPUT :

    IPRF,IPZ,EIPRF,EIPZ,CORREL : Impact parameters with errors and
              correlations.

IMPLICIT INPUTS:

    none

IMPLICIT OUTPUTS:

    none

CALLED BY :

ZAUCIP, Calculate Impact Parameter (see 4.6.5). ZAUSER (see 4.5.10).

CALLED ROUTINE(S):

ZUGAUS (see 4.7.13)

(To get a GAUSsian random number.)

TBDCA2

(To call slightly hacked version of DELPHI routine TBDCAE (the actual calculation of the IMPACT PARAMETER))

UCOPY

(CERNLIB routine.)

SIDE EFFECTS:

none

AUTHORS:

M. Berggren, LAL

CREATION DATE:

27-jul-1992