Hi,
here is the result of my investigation in the references of my thesis.

The ssbar popping parameter is, in jetset, parj(2) and is also known as
gamma_s.

It has been measured by TASSO and JADE at center of mass energies between
12 and 36 GeV:


 A DETAILED STUDY OF STRANGE PARTICLE PRODUCTION IN E+ E- ANNIHILATION AT
HIGH-ENERGY.
By TASSO Collaboration (M. Althoff et al.). DESY-84-093, Sep 1984. 34pp.
Published in Z.Phys.C27:27,1985


 CHARGED PARTICLE AND NEUTRAL KAON PRODUCTION IN E+ E- ANNIHILATION AT
PETRA.
By JADE Collaboration (W. Bartel et al.). DESY 83/042, Jun 1983. 50pp.
Published in Z.Phys.C20:187,1983


The paper from Jade has also a plot (18a) which shows the extrapolation of
the jetset model down to sqrt(S)=3GeV (i.e. a jet energy -equivalent
to Mx - down to 1.5 GeV) compared with the data from MARK I

 K0 PRODUCTION IN E+ E- ANNIHILATION.
By V. Luth et al.
 SLAC-PUB-1947, LBL-6465, Jun 1977. 14pp.
Published in Phys.Lett.B70:120,1977

The scaling seems to be ok down to our energies.

The results of the two papers are

gamma_s=0.35+/-0.05    Tasso
gamma_s=0.27+/-0.06    Jade

To account for extrapolation errors I would take as 1 sigma interval the
sum of the two intervals, gamma_s=0.21-0.40, i.e. a 30% error on this
parameter.


So the suggestion is to do the systematic error on ss~ popping varying by
100% the resonant component and by 30% the non resonant one
	ciao
	ric