We perform a momentum-space calculation of the reaction pp ! pp 0 near threshold. Direct production and pion rescattering are taken into account. For the latter a T-matrix obtained from a microscopic model of the N interaction is employed.The e ects of some approximations commonly used in studies of pp ! pp 0 are discussed. We nd that those approximations overestimate the cross section and also modify its energy dependence. We obtain a signi cant contribution from rescattering, but not nearly enough to describe the data.

Irrespective of the smoking status, increased mean BOP in SPT patients relates to disease severity and periodontal instability while smokers demonstrate lower mean BOP concomitantly with an increased prevalence of residual PPDs.

A microscopic model for the N N → ππ process is presented in the meson exchange framework, which in the pseudophysical region agrees with available quasiempirical information. The scalar (σ) and vector (ρ) piece of correlated two-pion exchange in the pion-nucleon interaction is then derived via dispersion integrals over the unitarity cut. Inherent ambiguities in the method and implications for the description of pion-nucleon scattering data are discussed.

We determine the πN N and πN ∆ formfactors from the P 11 resp. P 33 partial wave of πN scattering by dressing corresponding bare vertices with the help of πN non-pole contributions. The underlying model is based on meson exchange, and involves nucleon and delta-isobar pole and crossed-pole terms together with correlated ππ-exchange in the J P = 0 + (σ) and 1 − (ρ) channel. The results are very similar for πN N and πN ∆ and can be roughly parametrized by a monopole with cutoff mass ∼ > 500 MeV, with some variation due to model dependencies. Thus the formfactors are much less soft than derived before for the πN N case by Saito and Afnan using the same procedure but different πN interaction models.Typeset using REVT E X 1

We evaluate the contribution of second order terms to the pionnucleus s-wave optical potential of pionic atoms generated by short range nuclear correlations. The corrections are sizeable because they involve the isoscalar s-wave πN amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one.In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together: lowest order, Pauli corrected rescattering term, second order absorptive effects, terms from the interaction of pions with the virtual pion cloud (chiral corrections) and correlation effects. Different off-shell extrapolations for the πN amplitude are used and it is found that, although some individual terms are sensitive to the extrapolation, the sum of them is rather insensitive. The results are compared with empirical values from best fits to the data and are found to be compatible, within theoretical and empirical uncertainties. The results do not rule out further contributions but they put stringent constraints on their strength.

The ORPHEUS dark matter detector is operating at our underground laboratory in Bern (70 m.w.e.). The detector relies on measuring the magnetic flux variation produced by weakly interacting massive particles (WIMPs) as they heat micron-sized superheated superconducting tin granules (SSG) and induce superconducting-tonormal phase transitions. In an initial phase, 0.45 kg of tin granules in a segmented detector volume have been used. In this paper a general description of the experimental set-up, overall performance of the detector, and first results are presented.