arXiv subjects

S. Steininger

Publications and source records attributed to S. Steininger.

5 recordsLinked to original sources

arXiv1998

Strange magnetism in the nucleon

Using heavy baryon chiral perturbation theory to one loop, we derive an analytic and parameter-free expression for the momentum dependence of the strange magnetic form factor of the nucleon $G_M^{(s)} (Q^2)$ and its corresponding radius. This should be considered as a lower bound. We also derive a model-independent relation between the isoscalar magnetic and the strange magnetic form factors of the nucleon based on chiral symmetry and SU(3) only. This gives an upper bound on the strange magnetic form factor. We use these limites to derive bounds on the strange magnetic moment of the proton from the recent measurement of $G_M^{(s)} (Q^2=0.1 GeV^2)$ by the SAMPLE collaboration. We stress the relevance of this result for the on-going and future experimental programs at various electron machines.

hep-ph↗

arXiv1997

Working group on $ππ$ and $π$N interactions - Summary

This is the summary of the working group on $ππ$ and $π$N interactions of the Chiral Dynamics Workshop in Mainz, September 1-5, 1997. Each talk is represented by an extended one page abstract. Some additional remarks by the convenors are added

hep-ph↗

arXiv1997

Isospin violation in pion-nucleon scattering

We construct the complete effective chiral pion-nucleon Lagrangian in the presence of virtual photons to one loop. As an application, we consider strong and electromagnetic isospin violation for scattering of neutral pions off nucleons. We show that for the scattering lengths these isospin violating terms are of the same size as the purely hadronic ones. We also analyze isospin-violating effects for the $σ$--term. These can be as large as 10% for the absolute value but are negligible for the shift to the Cheng-Dashen point.

hep-ph↗

arXiv1997

Virtual photons in SU(2) chiral perturbation theory and electromagnetic corrections to $ππ$ scattering

We construct the generating functional of two flavor chiral perturbation theory including the effects of virtual photons in the one loop approximation. As an application, we calculate the electromagnetic corrections to the elastic $ππ$ scattering amplitude, in particular to its S--wave threshold parameters. Numerical estimates are given for the reaction $π^0 π^0 \to π^0 π^0$. These electromagnetic effects are found to be smaller than the hadronic two-loop corrections for the scattering length $a_0$. The effective range $b_0$ increases by 36% due to the unitary cusp.

hep-ph↗

arXiv1997

Baryon magnetic moments in chiral perturbation theory

We consider the chiral expansion of the octet baryon magnetic moments in heavy baryon chiral perturbation theory including all terms which are of order $q^4$. These terms are formally of quadratic order in the quark masses. We show that despite the large non-analytic quark mass corrections to the Coleman-Glashow relations at order $q^3$, including all analytic and non-analytic corrections at order $q^4$, which in total are of moderate size, allows for a fit to the measured magnetic moments due to the appearance of counter terms with free coupling constants of natural size. In this scheme, the $ΛΣ^0$ transition moment is predicted to be $μ_{ΛΣ^0} = (1.42 \pm 0.01) μ_N$.

hep-ph↗