4.4.10 SUBROUTINE ZTTRIP(P, V, TRIPRP, TIPZ, PHIIP) : calculate Impact Parameter

This routine calculates the impact-parameter in Rphi and z, with geometrical sign, from the momentum of a track (p) and a point on its trajectory (v). It also gives the phi angle of the point of closest approach to the origin of the projection of the track in the x-y (i.e. R phi) plane.

ARGUMENTS:

INPUT :

    P : 3-momentum of the track (in GeV)
    V : The point where P is given (in cm).

OUTPUT :

    TRIPRP : Impact parameter in Rphi (cm)
    TIPZ : Impact parameter in z (cm)
    PHIIP : Phi angle of point of closest approach (Radians)
    All of these will be set to zero for tracks along the z-axis

IMPLICIT INPUTS:

    From /PXCONS/ : BMAG, the magnetic field; CONSA, Speed of light.

IMPLICIT OUTPUTS:

    none.

CALLED BY :

ZTTCYL, Track intersect with CYLinder (see 4.4.6). ZTTPLA, Track intersect with PLAne (see 4.4.8). ZADECD, DECoDe data (see 4.5.5).

CALLED ROUTINE(S):

VDOT,VMOD,VUNIT

(CERNLIB routines)

SIDE EFFECTS:

none

AUTHORS:

M. Berggren, LAL

CREATION DATE:

27-jul-1992