
                   Program "xCOLOR". User's Manual.
                   --------------------------------

                             A.Kryukov

                   Institute for Nuclear Physics
                      Moscow State University
                      119899, Moscow, RUSSIA
                    E-mail: kryukov@npi.msu.su
                    Phone/Fax: (095) 939-0397


                             Abstract

       Program "xCOLOR" is intended for calculation the colour
       factor  in  non-abelian  gauge  field  theories.  It is 
       realized Cvitanovich algorithm [1]. In comparision with
       "COLOR" program [2] it was  made many improvements. The
       package was  writen by  symbolic mode.  This version is
       faster then [2] more then 10 times.



  After load the program by the following command

          load xcolor;

user can be able to use the next additional commands and operators.

Command SUdim.
--------------

Format:  SUdim <any expression>;

Set the order of SU group.
The default value is 3, i.e. SU(3).

Command SpTT.
-------------

Format:  SpTT <any expression>;

Set the normalization coefficient A: Sp(TiTj) = A*Delta(i,j).
Default value is 1/2.

Operator QG.
------------

Format:  QG(inQuark,outQuark,Gluon)

Describe the quark-gluon vertex. Parameters may be any identifiers.
First and second of then must be in- and out- quarks correspondently.
Third one is a gluon.

Operator G3.
------------

Format:  G3(Gluon1,Gluon2,Gluon3)

Describe the three-gluon vertex. Parameters may be any identifiers.
The order of gluons must be clock.

   In terms of QG and G3 operators you input diagram in "color" space as
a product of these operators. For example.

            Diagram:                    REDUCE expression:

                e1
            ---->---
           /        \
          |     e2   |
        v1*..........*v2    <===>   QG(e3,e1,e2)*QG(e1,e3,e2)
          |          |
           \    e3  /
            ----<---

Here:  --->---     quark
       .......     gluon

More detail see [2].




                      References.
                      -----------

[1] P.Cvitanovic, Phys. Rev. D14(1976), p.1536.
[2] A.Kryukov & A.Rodionov, Comp. Phys. Comm., 48(1988), pp.327-334.

   Any remarks send to

                             A.Kryukov

                   Institute for Nuclear Physics
                      Moscow State University
                      119899, Moscow, RUSSIA
                    E-mail: kryukov@npi.msu.su
                    Phone/Fax: (095) 939-0397


   Good luck!

