4.3.15 SUBROUTINE ZDROPA(FIRST, PB, ABSPA, COSTHE, SINTHE, POUT) : ROtate PAir

Assuming that the absolute value of the momentum of a particle (gamma or electron) after brems-strahlung or pair-production is known, as well as the 3-momentum vector of the initial particle (electron or photon), this routine calculates the 3-momentum vector of the particle after radiation. If FIRST is true, the azimuthal angle around the original direction is generated as well (isotropically).

ARGUMENTS:

INPUT :

    FIRST : .TRUE. -> generate phi
            .FALSE. -> use stored phi
    PB : 3-momentum of the particle before the interaction (in GeV/c)
    ABSPA : absolute value of the 3-momentum of the radiate
            particle (gamma or electron) (in GeV/c)
    COSTHE,SINTHE : cosine and sine of the angle between the line of
            flight of the particle before the interaction and the created
            particle.

OUTPUT :

    POUT : 3-momentum of the created particle (in GeV/c)

IMPLICIT INPUTS:

    none.

IMPLICIT OUTPUTS:

    none.

CALLED BY :

ZDMBRM (see 4.3.13). ZDMPAR (see 4.3.14).

CALLED ROUTINE(S):

ZURECT (see 4.7.14)

(To get a RECTangular random-number)

VDOT,VSCALE,VUNIT

(CERNLIB routines)

SIDE EFFECTS:

none

AUTHORS:

M. Berggren, UFRJ (adopted from DELSIM's SXRDEL)

CREATION DATE:

31-mar-1996