Short instructions:

I. Define a particle and put:
  (1) zeros as its decay modes and branching ratios;
  (2) some number in the first element of ubuf.

Example:

VEC/CREATE ubuf  R 2
VEC/CREATE nbuf  I 1
VEC/CREATE br(2) R 0. 0.
VEC/CREATE md(2) I 0  0
SPART 'Kpimunu' 4 0.4937E+00  1. 0.1237E-7 ubuf nbuf br md

The (1) force GEANT to call GUDCAY routine in the proper place (when a particle decays). The (2) will be used to say GUDCAY program what matrix element or another specific way of decay to use.

II. Add your code to GUDCAY program in IF(ubuf(1).EQ.your_number)...ENDIF clause. Be careful not to confuse with already used number (should be  clear from the GUDCAY code). Now GUDCAY contains Sasha Pastsiak code for decays K+ to mu+ nu gamma, K+ to e+ nu gamma according to corresponding matrix elements.
 

Changes done in CKMGEANT to incorporate that

1. uginit.F: A call was added to redefine an action routine for SPART command to ckmkuexe

2. ckmkuexe.F: command set was extended to include SPART command processing:
Now GSDK is called only if you put non zero values for decay branching rations and mode. Once we don't call GSDK GEANT will call GUDCAY program for the particle.

DV.