Eikonal description of nucleon-nucleon polarizations

Nucleon-nucleon elastic polarization data are analyzed within an eikonal framework in the range 6?plab?45 GeV/c and |t| 2.5 GeV/V². The isovector component is found to be dominated by a nearly exchange degenerate ρ-A₂ contribution while the isoscalar part requires both a lower lying Regge-pole exchange and an asymptotic pomeron contribution.     

Regge description of spin-spin asymmetry in photon diffractive dissociation

We explore the possibility to extract Δ(G(x) from a comparison of experimental data on the longitudinal spin-spin asymmetry A _LL in diffractive scattering of the heavy photon on the proton with calculations performed in perturbative QCD (pQCD). The data could be obtained at the HERA collider in scattering of polarized leptons off polarized protons. We have found a kinematic region where contributions to A _LL from soft processes are suppressed to guarantee an applicability of pQCD, hence the pQCD prediction can be reliably compared with data in this kinematic region.     

Regge phenomenology

A review is presented of Regge phenomenology in high energy two-body and quasi-two-body scattering.     

Logarithmic Regge pole

This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the begin{document}$ rho(s)$end{document}-parameter as well as to the elastic slope begin{document}$ B(s)$end{document} at high energies.     

Regge and Okamoto Symmetries

We will relate the surprising Regge symmetry of the Racah-Wigner 6 j symbols to the surprising Okamoto symmetry of the Painlevé VI differential equation. This then presents the opportunity to give a conceptual derivation of the Regge symmetry, as the representation theoretic analogue of the derivation in [5, 3] of the Okamoto symmetry.     

Double Regge exchange phenomenology

We construct a double Regge exchange amplitude which has the proper analytic structure and which is phenomenologically viable. The various couplings involved can be estimated using pole extrapolation techniques which are successful in two-body scattering. We explicitly calculate the double Regge exchange contributions to the well-measured, and related, processes K^±p → K⁰π^±p and π^?p → K^?K⁰p. In this way the observed features of the dimeson partial-wave production amplitudes are used to text the double-exchange approach.     

The short-range nucleon-nucleon repulsion

The short-range repulsion (0.2–0.4 fm) between nucleons is investigated. The opposing effects of ω-meson exchange and ε-meson (J^p = 0⁺) exchange are investigated, and the relation to Regge behaviour is demonstrated using fixed-s dispersion relations. The energy dependence of the short-range interaction is emphasized, and experimental data on polarization in elastic NN scattering at high energy are used to give the necessary coupling constant.     

Nonlocal nucleon-nucleon interaction JISP

The J-matrix inverse scattering formalism is described and a new type of nucleon-nucleon interaction JISP is constructed within its framework. Interaction for each partial NN scattering is represented by a small matrix in the oscillator basis, which allows its direct use in multiparticle shell-model calculations and in calculations within the resonating group approximation. The JISP reproduces np scattering data and deuteron characteristics with an accuracy of modern realistic NN potentials (x ²/datum = 1.05). The generalization of this interaction which takes into account violation of charge independence of nucleon-nucleon forces is proposed and pp scattering phases calculated with this new charge-dependent interaction CD-JISP are discussed.     

Bremsstrahlung in nucleon-nucleon collisions

The theory of bremsstrahlung in nucleon-nucleon collisions at non-relativistic energies is reviewed, with special emphasis on the possibility of drawing conclusions concerning the nucleon-nucleon interaction. The basic concepts are introduced in section 2, and illustrated in section 3 for the case of a separable interaction. Soft-photon theorems are discussed in section 4. Section 5 contains some brief comments on the comparison between theory and experiment. The theory needs a number of correction terms, which are discussed in section 6. A generalized Ward identity for bremsstrahlung, which relates the divergence of the contribution from internal lines to off-shell scattering amplitudes is also given.     

Comparing some nucleon-nucleon potentials

The aim is to compare a few Nucleon-Nucleon (NN) potentials especially Reid68, Reid68-Day, Reid93, UrbanaV14, ArgonneV18, Nijmegen 93, Nijmegen I and Nijmegen II. Although these potentials have some likenesses and are almost phenomenological, they include in general different structures and their own characteristics. The potentials are constructed in a manner that fit NN scattering data or phase shifts and are compared in this way. A high-quality scale of a potential is that it fits the data with χ²/N _data ≈ 1, describes well the deuteron properties and gives satisfactory results in nuclear-structure calculations. However, these scales have some failures. Here, we first compare many potentials by confronting them with the data. Then, we try to compare the potential forms by considering the potential structures directly and therefore regarding their substantial bases somehow. To do so, we note that since the potentials are written in different schemas, it is necessary to write them in a unique schema. On the other hand, because three major terms in the NN interaction are central, tensor and spin-orbit terms; so, to perform a reduction plan and arrive at a common structure, we choose the Reid’s potential form. Next, we compare the potentials for some states and address some other related issues as well.     

Equivalent nonlocal nucleon-nucleon potentials

The local nucleon-nucleon potential which contains a strong repulsive core is often replaced by an equivalent weak but non-local potential. Such potentials can be obtained by unitary transformations of the two-body Hamiltonian. Necessary and sufficient conditions are derived which must be fulfilled by the unitary transformations in order to give equivalent potentials. Special examples of unitary transformations with this property are investigated.     

Relaxation of polarisation

The relaxation of a wide range of solid dielectrics follows fractional power laws in frequency known as the universal or constant phase angle law. Instead of analysing the time dependence of the microscopic relaxations of dipoles or of charges in terms of the fluctuation dissipation theorem, we make use of the unique property of the universal law that the ratio of the macroscopic energy lost per radian to energy stored in the system under an alternating field drive is independent of frequency. We show that in solids a sufficient condition for this energy criterion to be satisfied is that the energy loss per microscopic reversal is the same regardless of the rate of reversals. The significance of this is discussed.     

Analytic model of Regge trajectories

A model for a Regge trajectory compatible with the threshold behavior required by unitarity and asymptotics in agreement with analyticity constraints is given in explicit form. The model is confronted in the time-like region with widths and masses of the mesonic resonances and, in the space-like region, the ρ trajectory is compared with predictions derived from the π-N charge-exchange reaction. Breaking of the exchange degeneracy is studied in the model and its effect on both the masses and widths is determined. Received: 23 January 2001 / Accepted: 9 February 2001