What happens at the end of the QCD cascades?
LU TP 97-36
Bo Andersson
Work done in Lund together with G. Gustafson and P.Sutton
ABSTRACT
This is a progress report on recent work done in Lund
to describe the final steps in the QCD coherent
bremsstrahlung cascades, with particular emphasis on the occurrence of
a size parameter c=11/6 in phase space. Two gluons,
being interacting vector particles, will due to helicity conservation
effectively stay apart a distance c,
counted in generalised rapidity (a notion which I will define in the text but
essentially corresponds to rapidity measured along the color flux lines
of the field between the gluons).
The same size c also occurs in the beta-function
as a measure of the region,
inside which a virtual gluon splitting via reabsorbtion in the
next step of perturbation theory will correspond to a ``loss-term'' in the
Callan-Symanzik equations. Our conclusion is that at the end of the cascades
when the dipole masses (M_d) are such that
2log(M_d/Lambda) is approximately n*c with n
a few units, then an ordered field
of a helix character will emerge, i.e. a set of
final ``screwy gluons'' are emitted in an ordered way in
rapidity and azimuthal angle around the
dipole axes so that the color lines are turning around.