16 research outputs found
On the Corrections to Dashen's Theorem
The electromagnetic corrections to the masses of the pseudoscalar mesons
and are considered. We calculate in chiral perturbation theory the
contributions which arise from resonances within a photon loop at order . Within this approach we find rather moderate deviations to Dashen's
theorem.Comment: 14 pages, sligthly enlarged version; a numerical error is corrected
and the embedding of the figures is improved. The complete paper, including
figures, is also available via anonymous ftp at
ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/; to be published in
Phys.Rev.
Resonance Contributions to the Electromagnetic Low Energy Constants of Chiral Perturbation Theory
The effective chiral Lagrangian of the strong and electromagnetic
interactions of the pseudoscalar mesons at low energies depends on a set of low
energy constants. We determine the contributions to the electromagnetic
coupling constants at order , which arise from resonances within a
photon loop. We give some implications of our results, in particular we discuss
in detail the effects on the corrections to Dashen's theorem.Comment: LaTex (uses epsfig.sty), 35 pages including 3 Postscript figures. The
complete paper is also available via anonymous ftp at
ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/ ; slightly enlarged
version. Accepted for publication in Nucl. Phys.
Virtual Photons in Chiral Perturbation Theory
In the framework of chiral perturbation theory virtual photons are included.
We calculate the divergences of the generating functional to one loop and
determine the structure of the local action that incorporates the counterterms
which cancel the divergences. As an application we discuss the corrections to
Dashen's theorem at order [e^2*m(quark)].Comment: 19 pages , LaTex, 1 figure appended as PostScript file, (little
corrections on the pages 8 and 17 - the physical results are not affected),
BUTP-94/
Rho - omega mixing in chiral perturbation theory
In order to calculate the rho - omega mixing we extend the chiral couplings
of the low-lying vector mesons in chiral perturbation theory to a lagrangian
that contains two vector fields. We determine the momentum dependence of the
two-point function and recover an earlier result for the on-shell expression.
We discuss the off-shell behaviour of the mixing.Comment: Latex, 12 pages. The paper is also available via anonymous ftp at
(129.13.102.139) ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-08/ttp95-08.ps,
or via www at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints
Extension of the Chiral Perturbation Theory Meson Lagrangian to Order
We have derived the most general chirally invariant Lagrangian
for the meson sector at order . The result provides an extension of the
standard Gasser-Leutwyler Lagrangian to one higher order,
including as well all the odd intrinsic parity terms in the Lagrangian. The
most difficult part of the derivation was developing a systematic strategy so
as to get all of the independent terms and eliminate the redundant ones in an
efficient way. The 'equation of motion' terms, which are redundant in the sense
that they can be transformed away via field transformations, are separated out
explicitly. The resulting Lagrangian has been separated into groupings of terms
contributing to increasingly more complicated processes, so that one does not
have to deal with the full result when calculating contributions to
simple processes.Comment: 59 pages in LaTex, using RevTex macro, TRIUMF preprint TRI-PP-94-6
Tau Decays and Chiral Perturbation Theory
In a small window of phase space, chiral perturbation theory can be used to
make standard model predictions for tau decays into two and three pions. For
, we give the analytical result for the relevant form
factor up to two loops, then calculate the differential spectrum and
compare with available data. For , we have calculated
the hadronic matrix element to one loop. We discuss the decomposition of the
three pion states into partition states and we give detailed predictions for
the decay in terms of structure functions. We also compare with low energy
predictions of meson dominance models. Overall, we find good agreement, but
also some interesting discrepancies, which might have consequences beyond the
limit of validity of chiral perturbation theory.Comment: 39 pages, Latex, including 8 Postscript figures. The complete paper
is also available via anonymous ftp at ftp://www-ttp.physik.uni-karlsruhe.de/
, or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprint