abstract

We describe our Monte Carlo quark-parton model of multiparticle production. The model is based on the following assumptions: mesons and baryons in the final state are originated by the recombination of quarks and antiquarks, the recombination is of a short range in rapidity and the valence quarks keep large momentum fractions during the collision. Low mass dimuons are supposed to arise from the annihilation of quarks and antiquarks (most of them created during the collision). Good qualitative agreement with data on low mass dimuon production is obtained if constraints following from the space-time evolution of the interaction are taken into account.

abstract

It is shown that equations of a vector field of general type and of an 8-component spinor field have the same matrix formulation. The internal symmetry group of these equations, which we called the dyal symmetry or the D-symmetry, is isomorphic to the O(3,1) group. The explicit form of finite dyal transformations is given. The transformations of the Pauli-Gursey group of the 4-component massless Dirac field are a particular case (O(3) subgroup) of dyal transformations.

abstract

The aim of this comment is twofold. Firstly, it is pointed out that the bag-like solution conjectured recently by H. Suura in the case of the relativistic Breit equation (in its primary form consistent with the single-particle theory) with an infinitely rising central potential is in fact a solution to a related inhomogeneous equation. One may speculate on a possible physical meaning of the source term there. Secondly, discontinuous solutions to the original homogeneous equation are constructed. In particular, they can be confined to the inner region \(r \leq r_0\) or restricted to the outer region \(r \geq r_0\), where \(V(r_0) = E\), but both kinds of solutions can be mixed by an additional interaction. The new solutions are normalized to the Dirac \(\delta \)-function and so belong to the continuous-energy spectrum, in contrast with the Suura solution which is normalizable in the usual sense. One may wonder if the new solutions have only a formal meaning.

abstract

The angular distributions for the reactions \(^{154}\)Sm(d,p), \(^{166}\)Er(d,p), \(^{170}\)Yb(d,p), \(^{176}\)Yb(d,p) and \(^{154}\)Sm(d,t), \(^{166}\)Er(d,t) have been measured at a deuteron energy of 12.08 MeV. The reaction products were analysed in a magnetic spectrograph or by means of a solid state detector. The angular distributions for particle groups corresponding to 66 levels in the final nuclei have been analysed in terms of the DWBA method. On this basis the transferred angular momentum 1 was determined and the Nilsson Model assignments of the levels were determined or confirmed. Several of the angular distributions deviate considerably from the calculated shapes. Possible reasons for these deviations are discussed

abstract

Padé approximation has been proposed for calculating the scattering length and the effective range as functions of the potential strength. The appropriate Taylor series coefficients which constitute input for the Padé method are obtained from a perturbative scheme based on the variable phase method.

abstract

Bohr and Mottelson simplification of the Valatin solution for the rotating harmonic oscillator potential is employed to the model analysis of the high angular momentum states in atomic nuclei. The resulting yrast line consists of several trajectories corresponding to fixed nucleonic configurations. Within each trajectory the system tends to acquire oblate, or sometimes prolate shape which is axially symmetric with respect to rotation axis. Dynamical i.e. resulting from the spectrum) moments of inertia turn out to be of the order of rigid moments for a given nuclear shape. There seems to be no possibility for the existence of yrast traps in the pure harmonic oscillator potential.