Mikolaj Sawicki

Attenuation of the flux of neutrachamps in the Earth's atmosphere-a parametric study

The authors estimate the attenuation of the flux of neutrachamps as they propagate through the Earths atmosphere and discuss the possibility that they will reach the surface of the Earth.

On the Nucleon Renormalization in Many Nucleon Problems Due to Pionic Degrees of Freedom

Conceptual problems of unified two-nucleon force models are discussed. The force models are based on the pion-nucleon vertex and attempt a description of the nucleon-nucleon interaction below and above pion threshold. The conceptual problems arise from the nucleon renormalization due to pionic degress of freedom. Keeping channels with a single pion only no renormalization procedure can be given which is consistent in the onenucleon and in the many-nucleon systems. The medium dependence of the one-pion exchange potential is illustrated. [NUCLEAR REACTIONS Nucleon renormalization in coupled NNnNN equations, inconsistencies of renormalization between oneand A-nucleon systems, energy dependence of one-pion exchange potential]

4-Nucleon scattering processes with unitary pole approximation

Abstract Generalized separable potential model of Alt, Grassberger and Sandhas is applied to 4-N system with the use of Bateman method and unitary pole approximation (UPA). Our principal aim is the evaluation of cross sections for processes like p 3He → p 3He and dd → pt. Bound states for 2-, 3-, and 4-body systems turned out to be very close to the experimental data either by input or by accident. However, the good fit at the negative energy, combined with the UPA method gave us a very good agreement for scattering processes at laboratory energies 9.75, 13.8, 25.3 and 51.5 MeV.

The v-v Sector of the Lee Model

The Schrödinger-equation in the V-V sector of the Lee model is investigated. We obtain a three-body Lippmann-Schwinger equation, with a new type of disconnectedness, and construct the resolvent operator by means of a modified Faddeev technique.

Interpolating between instant and light front dynamics

Abstract The “instant” and “light front” forms of relativistic dynamics postulated by Dirac refer to physical conditions on flat spacelike surfaces in the Minkowski space. We consider another flat surface in the Minkowski space that upon parametric rotation interpolates between “instant” and “light front” surfaces. A projection of the covariant perturbation theory on the new surface is then considered. One limit of the theory reproduces the usual instant dynamics, whereas a different limit gives a light front dynamics. Neither infinite momemtum frame limit nor infinite momenta are involved. Although the interpolating surface is the “instant” surface in the moving system of reference, we argue why our procedure should not be associated with a Lorentz transformation.

Application of Multichannel Scattering Theory to Pionic Reactions Within the Lee Model

Abstract The multichannel scattering theory is applied to the (2,2) sector of the (non-static) Lee model. Rigorous expressions for the transition amplitudes for two-fragments channels are derived. These expressions contain all effects of off-shell renormalization in a complete and consistent way. With suitable identification of the elementary fields of the model the reactions considered correspond to a simplified description of elastic proton-proton and pion-deuteron scattering and to pion absorption on the deuteron. We obtain a two-body equation for the description of the elastic proton-proton scattering and an extension of the two-potential formula for the pion-deuteron scattering, which can be cast into the form of the multiple-scattering series.