https://doi.org/10.1140/epja/i2017-12401-8
Regular Article - Theoretical Physics
The reactions 
and 
in 
PT with an isosinglet scalar resonance
1
Department of Chemistry and Physics, Franklin College, 46131, Franklin, IN, USA
2
Institute of Nuclear and Particle Physics and Department of Physics and Astronomy, Ohio University, 45701, Athens, OH, USA
* e-mail: phillid1@ohio.edu
Received:
16
June
2017
Accepted:
28
September
2017
Published online:
24
October
2017
The lowest-lying resonance in the QCD spectrum is the 
isoscalar 
-meson, also known as the 
. We augment SU(2) chiral perturbation theory (
PT) by including the -meson as an additional explicit degree of freedom, as proposed by Soto, Talavera, and Tarrús and others. In this effective field theory, denoted PTS, the -meson’s well-established mass and decay width are not sufficient to properly renormalize its self energy. At 
another low-energy constant appears in the dressed -meson propagator; we adjust it so that the isoscalar pion-pion scattering length is also reproduced. We compare the resulting amplitudes for the 
and 
reactions to data from threshold through the energies at which the -meson resonance affects observables. The leading-order (LO) 
amplitude reproduces the -meson pole position, the isoscalar scattering lengths and scattering and data up to 
GeV. It also yields a amplitude that obeys the Ward identity. The value obtained for the 
polarizability is, however, only slightly larger than that obtained in standard PT.
© SIF, Springer-Verlag GmbH Germany, 2017
