4.6.5 SUBROUTINE ZAUCIP(RFVTX, IPRFX, IPZX, EIPRFX, EIPZX, IPCORR, XYZRED, VCOVR) : Calculate Impact Parameter

Calculate the impact parameters wrt. the vertex of a track.

If RFVTX is true, the main vertex will be fitted without TRACK. This is to break the correlation between the vertex and the impact parameter. Takes time, but to get the right probabilities it should be done.

If the track is included in any jet, ZAUIMP is called requesting life-time signing, if it is not, geometric signing is instead requested. Hence, to get life-time signing, jet-clustering calling ZAUCLU must have been done before a call to ZAUCIP, and IJET in /ZAJET/ must have been set to the jet of the current track.

See further explanations in ZAUINP 4.6.6 .

ARGUMENTS:

INPUT :

    RFVTX : refit main vertex without TRACK.
            this is to break the correlation between
            the vertex and the impact parameter. takes time, but
            to get the right probabilities it should
            be done.

OUTPUT :

    IPRFX,IPZX,
    EIPRFX,EIPZX,
    IPCORR : Impact parameters in Rphi and z, their errors and
             correlation
    XYZRED : Main vertex position, without track TRACK
    VCOVR  : Main vertex covariance matrix, without track TRACK

IMPLICIT INPUTS:

     From /ZAEVT/ : XYZ & VCOV, fitted main vertex w/ errors; MTRK,
                    total number of seen tracks.
     From /ZATRS/ : TRACK, current track number; CHAS, charge of track;
                    INVTX, track in main vertex ?; PAR & WGT, track
                    parameters w/ weight mat at perigee;
                    PVEC, seen momentum of track.
     From /ZAJET/ : IJET, jet number of TRACK; PJETR, momentum of
                    jet; PHIJET, phi angle of jet.

IMPLICIT OUTPUTS:

    none.

CALLED BY :

ZAURST, Reject Strange particle decay products (see 4.6.3). ZAUSER (see 4.5.10).

CALLED ROUTINE(S):

ZAUVF2 (see 4.6.2)

(To do Vertex Fit 2.)

ZAUIMP (see 4.6.6)

(To get IMpact Parameter.)

UCOPY,VMOD,VDOT

(CERNLIB routines.)

SIDE EFFECTS:

none.

AUTHORS:

M. Berggren, UFRJ

CREATION DATE:

05-APR-1995