4.3.10 SUBROUTINE ZDPAIR(LAYLIS, PP, PMINPA, KKK, DST, NNEW) generate PAIR production

This routine decides if a pair-production process occurs while the photon with momentum PP goes through the detector, and if so generates the process and updates the contents of LUJETS accordingly.

ARGUMENTS:

INPUT :

     LAYLIS : List of detector layers hit by particle :
              LAYLIS(1,i) = number of the i:th hit layer.
                            LAYLIS(2,i) tells if it is a  plane
                            or a cylinder, if it measures or not,
                            and if it is the reference layer.
              LAYLIS(2,i) = 0  : mathematical layer : no material,
                                 no measurement. Ignored in all
                                 calculations
                            1  : seen by a cylinder
                            2  : seen by a plane
                            -1 : particle went through a cylinder, but
                                 was not seen by the detector.
                            -2 : particle went through a plane, but
                                 was not seen by the detector.
                            10 : the layer is a reference cylinder
                            20 : the layer is a reference plane
              LAYLIS(3,i) = No. of radiation lengths in layer.
              LAYLIS(1,i) = -1 -> end of list.
    PP : 3-momentum of the incomming photon (in GeV/c)
    PMINPA : Minimum P of photon to consider pair-production.
    KKK : line-number of the incomming photon in LUJETS

OUTPUT :

    LAYLIS : List of detector layers hit by particle, updated if there
             was an interaction
    DST : Distance travled from VERT to the point of interaction.
          0.0 if no interaction.
    NNEW : number of new particles generated :
             0 : no interaction
             2 : A interaction took place, the gamma marked as
                 decayed, new electron and positron inserted into
                 LUJETS.

IMPLICIT INPUTS:

    From /ZXEVT/ ANC, ancestor of initial particle;

IMPLICIT OUTPUTS:

    To /LUJETS/ P, momentum of created particles; V, production-point
       of created particles; K, id. and decay info of initial and
       created particles; NLUND, total number of particles.

CALLED BY :

ZDETSI, DETector SImulation (see 4.3.1).

CALLED ROUTINE(S):

ZTTINF (see 4.4.48)

(To get Track INFo at a layer)

ZTPX0 (see 4.4.45)

(To get number of X0:s of a plane)

ZTCX0 (see 4.4.44)

(To get number of X0:s of a cylinder)

ZTPANB (see 4.4.47)

(To get Plane Atom number)

ZTCANB (see 4.4.46)

(To get Cylinder Atom number)

ZDLPAR (see 4.3.12)

(To get Lambda for PAiR-production)

ZDMPAR (see 4.3.14)

(To Make a e+e- PAiR)

ZDELLY (see 4.3.16)

(To DELete LaYers)

VMOD

(CERNLIB routine)

SIDE EFFECTS:

none

AUTHORS:

M. Berggren, UFRJ

CREATION DATE:

05-may-1996