DOI: 10.1140/epja/i2002-10052-6
Chiral magnetism of the nucleon
T.R. Hemmert1, 2 and W. Weise1, 31 Physik Department, Theoretische Physik, Technische Universität München, D-85747 Garching, Germany
2 Nuclear Theory Group (Visiting Scholar.) , Department of Physics, University of Washington, Seattle, WA 98195, USA
3 ECT*, Villa Tambosi, I-38050 Villazzano (Trento), Italy
themmert@physik.tu-muenchen.de
weise@ect.it
(Received: 23 April 2002 / Revised version: 17 July 2002 / Published online: 17 December 2002)
Abstract
We study the quark mass expansion of the magnetic moments
of the nucleon in a chiral effective field theory including
nucleons, pions and delta-resonances as explicit degrees of
freedom. We point out that the usual power counting applied so far
to this problem misses important quark mass structures generated via
an intermediate isovector
M1 nucleon-delta transition. We propose
a modified power counting and compare the resulting chiral
extrapolation function to available (quenched) lattice data. The
extrapolation is found to work surprisingly well, given that the
lattice data result from rather large quark masses. Our calculation
raises the hope that extrapolations of lattice data utilizing chiral
effective field theory might be applicable over a wider range in
quark masses than previously thought, and we discuss some open
questions in this context. Furthermore, we observe that within the
current lattice data uncertainties the extrapolations presented here
are consistent with the Padé fit ansatz introduced by the Adelaide
group a few years ago.
11.10.-z - Field theory.
12.38.Gc - Lattice QCD calculations.
11.30.Rd - Chiral symmetries.
© Società Italiana di Fisica, Springer-Verlag 2002
