In this paper we study the interactions of observed pions with inferred scalar σ meson [1,2] and fermion quark SU(2) fields in a chiral-invariant manner at low energies. Specifically we consider two chiral theories: a) A chiral quark model (CQM) dynamically inducing [2] the entire quark-level SU(2) linear σ model (LσM) but depending on no free parameters. b) Chiral perturbation theory (ChPT) in...

We study the direct CP violation induced by inelastic final state interaction (FSI) rescattering in D → ππ modes, and find that the resultant CP asymmetry is about 10 which is larger than ǫ in the K-system. Our estimation is based on well-established theories and experiment measured data, so there are almost no free parameters except the weak phase δ13 in the CKM matrix. PACS number(s): 11.30.E...

In the first part of the talk, I discussed the nature of the effective theory that describes the properties of the pion-nucleon-interaction at low energies, using the static model as a starting point. In the second part, I then pointed out that the infrared singularities occurring in the πN scattering amplitude are stronger and of a more complex structure than those encountered in ππ scattering...

The contribution of a ππ-exchange three-body force to the three-nucleon binding energy is calculated in terms of a πN amplitude. The latter is based on a meson-theoretical model of πN interaction developed by the Jülich group. Similar to a previous study based on simple phenomenological πN potentials a very small effect of the resulting three-body force is found. Possible origins of the two-ord...

The DIRAC spectrometer has been commissioned at CERN with the aim of detecting ππ atoms produced by a 24 GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum, and the measurement of the latter with resolution around 0.6 MeV/c. The general character...