Related papers: Quark effects and isospin-violation in ${}1S_0$ NN…
We present an analysis of isospin-breaking effects in threshold pion-nucleon scattering due to the light quark mass difference and the dominant virtual photon effects. We discuss the deviation from various relations, which are exact in the…
The charge symmetry breaking and charge independence breaking N-N ^1S_0 scattering length differences, Delta a_{CSB} and Delta a_{CIB}, are calculated by a resonating group method with a quark cluster model. By adding the QED-QCD…
Isospin symmetry is explicitly broken in the Standard Model by the mass and electric charge of the up and down quarks. These effects represent a perturbation of hadronic amplitudes at the percent level. Although these contributions are…
We calculate isospin breaking in pion-nucleon scattering in the threshold region in the framework of covariant baryon chiral perturbation theory. All effects due to quark mass differences as well as real and virtual photons are consistently…
We investigate isospin breaking in low-energy pion-nucleon scattering in the framework of chiral perturbation theory. This work extends the systematic analysis of [1] to the energy range above threshold. Various relations, which identically…
We present results on the pseudoscalar meson masses from a fully dynamical simulation of QCD+QED. We concentrate particularly on violations of isospin symmetry. We calculate the $\pi^+$-$\pi^0$ splitting and also look at other isospin…
We analyze isospin breaking through quark mass differences and virtual photons in the pion-nucleon scattering lengths in all physical channels in the framework of covariant baryon chiral perturbation theory. The so-called triangle relation…
We study electromagnetic as well as strong isospin breaking effects in the isospin mass splittings of light pseudoscalar and vector mesons. To this end we employ a coupled system of quark Dyson-Schwinger and meson Bethe-Salpeter equations…
In the first part of these lectures, I consider chiral perturbation theory in the presence of matter fields. It allows to systematically work out the consequences of the broken chiral symmetry of QCD. As examples, threshold pion photo- and…
While electromagnetic and up-down quark mass difference effects on octet baryon masses are very small, they have important consequences. The stability of the hydrogen atom against beta decay is a prominent example. Here we include these…
The isospin symmetry breakings of q{\bar q} are investigated in the QCD sum rule method. The electromagnetic effects are evaluated following the procedure requiring that the electromagnetic effects for charged meson be gauge invariant. We…
We present a new method to evaluate with high precision the isospin breaking effects due to the mass difference between the up and down quarks using lattice QCD. Our proposal is applicable in principle to any hadronic observable which can…
Isospin symmetry is well fulfilled in the QCD vacuum, as evidenced by small mass differences of isospin partners and suppressed isospin-violating decays. Recently, the NA61/SHINE collaboration reported an unexpectedly large…
Interactions of charmed and strange mesons with baryonic matter can be calculated in the nonrelativistic quark potential model. For KN scattering data exists, and the theoretical results for S-waves are in approximate agreement with…
The spin effects at high energies and momenta transferred $|t|>1 GeV^2$ are analysed for quark-photon scattering. The energy independence of the ratio of spin-flip and spin-non-flip amplitudes in the same $\alpha_s$ order of QCD is…
We discuss the electromagnetic corrections to the pion-nucleon scattering lengths generated by minimal e. m. coupling from a knowledge of the low energy expansion of the pion-nucleon elastic scattering amplitude as well as from the nucleon…
We consider pion-nucleon scattering in heavy-baryon chiral perturbation theory to third order. All electromagnetic corrections appearing to this order are included. We thus have a consistent description of strong and electromagnetic…
Although SU(2) isospin symmetry is generally assumed in the basic theory of the strong interaction, a number of significant violations have been observed in scattering and bound states of nucleons. Many of these violations can be attributed…
We discuss the separation of isospin-symmetric and isospin-breaking contributions in the hadronic observables within the framework of QCD plus QED. Further, we briefly review some recent work on the low-energy hadron phenomenology, in which…
I discuss recent progress made in calculating electromagnetic corrections in the framework of the effective field theory of QCD. In the case of elastic pion-pion scattering, strong interaction predictions have been worked out to two loop…