Hadronic quark distribution amplitudes from QCD sum-rule moments

We discuss the reliability of hadronic wave functions (quark distribution amplitudes) determined by a finite number of QCD sum-rule moments. Although the expansion coefficients for polynomial models of the wave function are uniquely determined by the moments, the inherent uncertainty in such moments leads to a considerable indeterminacy in the wave functions because minimal changes of the moments can lead to large oscillations of the model function. In particular, the freedom in the moments left by QCD sum rules leads to a nonconverging polynomial expansion. This remains true even if additional constraints on the wave functions are used. As a consequence of this, the widely used procedure of constructing polynomial models of hadronic wave function from QCD sum rule moments does not guarantee even a reasonable approximation to the true wave function. The differences among the model wave functions persist also in the calculations of physical observables like hadronic form factors. This implies that physical observables calculated by means of such model wave functions are in general very unreliable. As specific examples, we examine the pion and nucleon wave functions and show that Gegenbauer as well as Appell polynomial expansions constructed from QCD sum rule moments are ruled out. The implications for the wave functions which are generally used in the literature are discussed.     

Polarization phenomena in NN ↔ Dπ reactions

On the basis of a relativistic approach, NN ? Dπ reactions are analyzed in detail. The coherent sum of one-nucleon-exchange and pion-rescattering diagrams is calculated. It is shown that polarization observables are highly sensitive to off-mass-shell effects within the deuteron and that some of these observables can change sign upon taking these effects into account. The effect of the deuteron P wave is also investigated. The results obtained by calculating a full set of observables are compared with experimental data on the reaction pp → Dπ ⁺.     

Ergodical time evolution of a Gaussian wave packet in quantum dots

The time evolution of a Gaussian wave packet (GWP) confined in a quantum dot is numerically studied. The quantum dots are modelled by a two-dimensional square box and by the potential x⁴ + y⁴. For the case of an incommensurate energy spectrum the time evolution of observables has no global period. As a result this leads to ergodic phase portraits with a finite phase volume. For the spatially wide GWP the distribution function of quantum observables may be approximated as a Gaussian one. For the case of commensurate transition frequencies in the quantum well the time evolution of observables is periodical and the phase portraits have a zero phase volume.     

Influence of the time-step on the production of free nucleons and pions from heavy-ion collisions around 1 GeV/nucleon

By considering different values of the time-step for the potential updates in the ultra-relativistic quantum molecular dynamics(UrQMD) model, we examine its influence on observables, such as the yield and collective flow of nucleons and pions from heavyion collisions around 1 GeV/nucleon. It is found that these observables are affected to some extent by the choice of the time-step,and the impact of the time-step on the pion-related observables is more visible than that on the nucleon-related ones. However,its effect on the π-/π+yield ratio and elliptic flow difference between neutrons and protons, which have been taken as sensitive observables for probing the density-dependent nuclear symmetry energy at high densities, is fairly weak.     

The effects of the microscopical theory of the Coriolis forces on nuclear beta-decay155Eu →155Gd

The wave functions yielded by the microscopical non-adiabatic treatment of the Coriolis interaction proposed in Dubna by Pyatov, Chernej and Baznat have been used in order to calculate the beta decay observables of some allowed transitions of the¹⁵⁵Eu nucleus. The Coriolis interaction effects are important especially for the absoluteft values (an important improvement is obtained) and for theβ-γ circular polarization correlation.     

CP-violating correlations in the reactione + e −»hadrons

We investigateCP-violating observables involving jets in the processe ⁺ e ^–»hadrons. These observables are sensitive to sources ofCP-violation beyond the standard model. We use an effective Lagrangian approach to parametrize possible newCP-violating interactions. Bounds on electric and weak diple moments of leptons and quarks are discussed.     

A novel method for solving the three-body scattering problem

A numerical scheme for solving a three-body scattering problem within the framework of the configuration space Faddeev equations in three-dimension, i.e., without resort to explicit partial wave expansion, is presented. The method is applied to calculate the low-energy n-d observables.     

Probabilistic Time

The concept of time emerges as an ordering structure in a classical statistical ensemble. Probability distributions p _τ (t) at a given time t obtain by integrating out the past and future. We discuss all-time probability distributions that realize a unitary time evolution as described by rotations of the real wave function $q_{\tau}(t)=\pm \sqrt{p_{\tau}(t)}$ . We establish a map to quantum physics and the Schr?dinger equation. Suitable classical observables are mapped to quantum operators. The non-commutativity of the operator product is traced back to the incomplete statistics of the local-time subsystem. Our investigation of classical statistics is based on two-level observables that take the values one or zero. Then the wave functions can be mapped to elements of a Grassmann algebra. Quantum field theories for fermions arise naturally from our formulation of probabilistic time.     

Neutrino magnetic moment solution for the solar neutrino problem and the SNO experiment

The motivations for the magnetic moment solution to the solar neutrino problem are briefly reviewed and the expected values for a number of observables to be measured by the SNO experiment are calculated assuming three different solar magnetic field profiles. The observables examined are the charged current event rate, the ratio of the neutral current to the charged current event rates and the charged current electron spectrum as well as their first and second moments. The dependence of results on the hep neutrino flux is also analysed and a comparison is made with the corresponding oscillation results.     

Equilibrium properties of the cubic phases of cobalt

Lattice constants and magnetic moments of face-centered cubic (fcc) and body-centered cubic (bcc) phases of cobalt obtained from self-consistent spin-polarized total-energy calculations by the augmented spherical wave method are compared to measurements. The calculated lattice constants fit the measured values of both phases to about 1%, but favor one of the two reported results on the newly-synthesized bcc phase. However the reported magnetic moments are substantially lower than the theoretical value for the bcc phase. We show that bcc cobalt is metastable up to 400 kbars pressure and, like fcc cobalt, is a strong ferromagnet. The magnetic moment of fcc cobalt is shown to collapse at a 5% lattice compression.     

System size dependence of particle production at the SPS

Recent results on the system size dependence of net-baryon and hyperon production as measured at the CERNSPS are discussed. The observed N _part dependences of yields, but also of dynamical properties, such as average transverse momenta, can be described in the context of the core corona approach. Other observables, such as antiproton yields and net-protons at forward rapidities, do not follow the predictions of this model. Possible implications for a search for a critical point in the QCD phase diagram are discussed. Event-by-event fluctuations of the relative core to corona source contributions might influence fluctuation observables (e.g., multiplicity fluctuations). The magnitude of this effect is investigated.     

Polarization phenomena in hadronic reactions

Predictions are made in the framework of the effective color field (ECF) model for polarization observables in $p + A \to \bar \Lambda X$ , A + A → ΛX and p + Pb → pX reactions. The predictions can be checked in the polarization experiments at IHEP (SPASCHARM), JINR (NICA) and BNL (RHIC). Estimates of quark masses and anamolous chromomagnetic quark moments are given.     

Effect of meson exchange corrections on allowed muon capture

Corrections to the impulse approximation calculation of the γ?ν angular correlation coefficient and recoil nuclear polarization in allowed muon capture transitions, arising from meson exchange effects, are studied and the value for the induced pseudoscalar coupling consistent with both observables is found to be (13.3 + 3)_gA, to a large extent free from nuclear wave function uncertainties.     

On the Parametrization of Low-Energy Parity-Violating Observables

The parity-violating (PV) two-nucleon interaction, unlike the parity-conserving one, is still poorly constrained. Recently such study in few-body systems has attracted quite some attention, as experiments become more feasible and theoretical calculations can be done reliably. It is found that using the so-called Danilov parameters, which are the zero-energy S–P transition amplitudes, yield a model independent way to parametrize low-energy PV observables. This provides not only a common interface through which calculations using different frameworks can communicate, but also helps to distinguish for which observables the contributions from higher partial waves can no longer be ignored.