DOI 10.1007/s100529800955
Reanalysis of the Das et al. sum rule
and application to chiral O(p4) parameters
B. Moussallam
I.P.N., Division de Physique Théorique, Université Paris-Sud, F-91406 Orsay Cédex (e-mail: moussall@ipno.in2p3.fr)
Received: 17 April 1998 / Published online: 16 September 1998
Abstract
A sum rule due to Das et al. is reanalyzed using a euclidian space
approach and a Padé resummation procedure.
It is shown that the result is essentially determined by the matrix elements
of dimension six and dimension eight operators which have recently been
measured by the ALEPH collaboration.
The result is further improved by using the vector spectral function which
must be extrapolated to the chiral limit.
This extrapolation is shown to be reliably performed under the
constraint of a set of sum rules.
The sum rule is employed not
as an approximation to 
but as an exact result for a
chiral low-energy parameter. A sufficiently precise evaluation
provides also an estimate for a combination
of subleading electromagnetic low-energy parameters.
Copyright Springer-Verlag
