We have analyzed low-energy pion-nucleon data for isospin invariance by comparing chargeexchange amplitudes derived from charge-exchange data with those predicted from recent~p elastic data through the application of isospin invariance. A discrepancy of the order of 7% is observed beyond the contributions of the~p Coulomb interaction and the hadronic mass differences. PACS numbers: 13.75.Gx, 24.80.Dc, 25.80.Gn fcEx = Of the eight reactions of the form~N~' N' the only three directly accessible experimentally are those with charged pion beams and proton targets: 7Tp elasticscattering, with amplitudes f, and 7r p~~" n chargeexchange (CEX) scattering, with amplitude fcEx. Isospin conservation gives a relationship among these three amplitudes, the triangle identity

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The energy dependence of forward pion double charge exchange reactions on light nuclei is studied for both the Ground State transition and the Double-Isobaric-Analog-State transitions. A common characteristic of these double reactions is a resonance-like peak around 50 MeV pion lab energy. This peak arises naturally in a two-step process in the conventional pion-nucleon system with proper handling of nuclear structure and pion distortion. A comparison among the results of different nuclear structure models demonstrates the effects of configuration mixing. The angular distribution is used to fix the single particle wave function. PACS: 25.80Gn, 24.10Ht,21.60Fw

We have performed a partial-wave analysis of K + -nucleon scattering in the momentum range from 0 to 1.5 GeV/c addressing the uncertainties of the results and comparing them with several previous analyses. It is found that the treatment of the reaction threshold behavior is particularly important. We find a T=0 scattering length which is not consistent with zero, as has been claimed by other analyses. The T=0 phase shifts for ℓ > 0 are consistent with a pure spin-orbit potential. Some indications for the production of a T=0 pentaquark with spin-parity D5/2+ are discussed.

We have analyzed recent data for pion elastic scattering on the three-nucleon system to extract the relative neutron-proton radii in 'He and H. Using standard multiple-scattering analysis techniques we determine the difference between the odd radii with an uncertainty of +0.007 fm and that between the even radii within +0.010 fm from the existing data. Additional data and improvements in the scattering theory can be expected to lead to a more precise determination.To assess the significance of the extracted radius differences we compare them with radii determined from Faddeev calculations that include charge-symmetry-breaking forces.