4.6.3 SUBROUTINE ZAURST(FORCE_REJECT) : Reject STrange particle decay products

This routine flags tracks that are likely to be form strange particle decays, from gamma conversions or from interactions in the detector. Strange particle decays are found by cutting around the K0 and lambda mass peaks (in addition to several other cuts), gamma conversions by calculating the probability that a pair is of such origin (routine GAMFIT), and other interactions by finding track pairs that cross each other close to material surfaces in the detector.

ARGUMENTS:

INPUT :

    FORCE_REJECT : bitted word. If bit i is set, then all tracks
            with history code i are flagged.

IMPLICIT INPUTS:

     From /ZAEVT/ : MTRK, total number of seen tracks;XYZ & VCOV,
                    fitted vertex pos w/ errors.
     From /ZATRS/ : ANC, true ancestor of tracks;
                    CL, true history class of tracks; JETNB, jet number of
                    tracks; PVEC, seen momentum of tracks; PAR & WGT,
                    track parameters w/ weight mat of tracks; CHA, charge of
                    tracks.

IMPLICIT OUTPUTS:

     To /ZATRS/ : CL, seen history class of tracks; INVTX, tracks
                  included in main vertex fit;

CALLED BY :

ZAUVF1, Vertex Fit 1 (or directly by ZAUSER) (see 4.6.1).

CALLED ROUTINE(S):

ZAUSTP (see 4.6.4)

(To check if STrange decay Product.)

ZUCINS (see 4.7.8)

(To Check if element IN Set)

ZAUIMP (see 4.6.6)

(To get IMpact Parameter.)

PXTCPX (see 4.7.4)

(To transform Track parameters on Cylinder to PXpypz)

GAMFIT

(To do GAMma conversion hypothesis FIT)

TKCIRC

(To get TracK intersection on CIRcle.)

ZTTCYL (see 4.4.6)

(To propagate Track to a CYLinder.)

UCOPY,VMOD,VSUB,VADD,DOTI,VDOTN

(CERNLIB routines)

SIDE EFFECTS:

none

AUTHORS:

M. Berggren, LAL

CREATION DATE:

27-jul-1992