Cumulative $${\pi}$$ -Mesons in $${}^{{12}}{C}{+}{}^{{9}}$$ Be-Interactions at 3.2 GeV/Nucleon

Physics of Atomic Nuclei - In the FRAGM experiment at the heavy-ion accelerator $$-$$ accumulator complex ITEP $$-$$ TWA, yields of cumulative charged $$\pi$$ mesons have been measured in a...     

Results of search for narrow diproton structures in thepn →ppπ − reaction at 1.98 GeV/c

The effective mass spectrum of two protons from the reactionp+n→pp+π ^?(backward) was investigated. The work was carried out at ITEP using a 3-meter magnet spectrometer and a proton beam of 1.98GeV/c momentum. Liquid deuterium was used as a target. The presented mass spectrum includes about 34000 events. No statistically significant signals from narrow dibaryons were found in the mass region 1.89–2.17GeV/c ²; the upper limits on narrow dibaryon production cross-section are given. At a mass of 1.8775GeV/c ² a narrow enhancement was found. A more detailed investigation of the observed phenomenon is needed.     

Higher order variational origin of the Dixonʼs system and its relation to the quasi-classical ‘Zitterbewegung’ in General Relativity

We show how the Dixon?s system of first order equations of motion for the particle with inner dipole structure together with the side Mathisson constraint follows from rather general construction of the ‘Hamilton system’ developed by Weyssenhoff, Rund and Grässer to describe the phase space counterpart of the evolution under the ordinary Euler–Poisson differential equation of the parameter-invariant variational problem with second derivatives. One concrete expression of the ‘Hamilton function’ leads to the General Relativistic form of the fourth order equation of motion known to describe the quasi-classical ‘quiver’ particle in Special Relativity. The corresponding Lagrange function including velocity and acceleration coincides in the flat space of Special Relativity with the one considered by Bopp in an attempt to give an approximate variational formulation of the motion of self-radiating electron, when expressed in terms of geometric quantities.     

Influence of a reaction medium on the oxidation of aromatic nitrogen-containing compounds by peroxyacids

The influence of different solvents on the oxidation reaction rate of pyridine (Py), quinoline (QN), acridine (AN), α-oxyquinoline (OQN) and α-picolinic acid (APA) by peroxydecanoic acid (PDA) was studied. It was found that the oxidation rate grows in the series Py < QN < AN, and the rate of the oxidation reaction of compounds containing a substituent in the α position from a reactive center is significantly lower than for unsubstituted analogues. The effective energies of activation of the oxidation reaction were found. It was shown that in the first stage, the reaction mechanism includes the rapid formation of an intermediate complex nitrogen-containing compound, peroxyacid, which forms products upon decomposing in the second stage. A kinetic equation that describes the studied process is offered. The constants of equilibrium of the intermediate complex formation (K _eq) and its decomposition constant (k ₂) in acetone and benzene were calculated. It was shown that the nature of the solvent influences the numerical values of both K _p and k ₂. It was established that introduction of acetic acid (which is able to form compounds with Py) into the reaction medium slows the rate of the oxidation process drastically. Correlation equations linking the polarity, polarizability, electrophilicity, and basicity of solvents with the constant of the PDA oxidation reaction rate for Py were found. It was concluded that the basicity and polarity of the solvent have a decisive influence on the oxidation reaction rate, while the polarizability and electrophilicity of the reaction medium do not influence the oxidation reaction rate.     

Synthesis and physico-chemical properties of composites based on nanostructured zinc oxide and polyaniline

Composites based on polyaniline and nanostructured zinc oxide were synthesized by mechanical mixing and the method of in situ polymerization and their physicochemical properties were studied. The electrical conductivity, surface structure and morphology of composites have been investigated. It is shown that the method of synthesis and quantity of filler affects the morphology and physicochemical properties of composite materials. An addition of various quantities of mineral filler to composite allows controlling conductivity of obtained materials. XRD-analysis of composite materials synthesized by in situ polymerization confirms the interaction of the components of the composite.     

Nuclear Fragments in the Interactions of Carbon Nuclei with a Beryllium Target at the Energy of 0.95 GeV per Nucleon

The differential cross sections for the yields of nuclear fragments at an angle of 3.5? in the fragmentation of carbon nuclei with energy 0.95 GeV per nucleon on a beryllium target were measured in the FRAGM experiment at the ITEP TWA heavy-ion accelerator. The momentum spectra of fragments were used to test the following four models of ion–ion interactions: BC, INCL++, LAQGSM03.03, and QMD. For light fragments, the slope parameters of the kinetic-energy spectra were obtained in the cumulative region.     

On an Application of the Lax-Phillips Scattering Approach in the Theory of Singular Perturbations

For a singular perturbation , n ≤ ∞, of a positive self-adjoint operator A ₀ with Lebesgue spectrum, the spectral analysis of the corresponding self-adjoint operator realizations A _T is carried out and the scattering matrix is calculated in terms of parameters t _ij under some additional restrictions on singular elements ψ _j . The results obtained enable one to apply the Lax-Phillips approach in scattering theory. __________ Published in Ukrains'kyi Matematychnyi Zhurnal, Vol. 57, No. 5, pp. 679–688, May, 2005.     

Yields of hydrogen and helium isotopes in fragmentation of carbon ions with the energy of 0.3 GeV/nucleon

Data on the yields of hydrogen isotopes (p, d, t) and helium isotopes (from ³He to ⁸He) at the angle of 3.5° in fragmentation of the carbon ions with the energy of 0.3 GeV/nucleon on the beryllium target are reported. The momentum spectra of the fragments in the rest frame of the fragmenting nucleus are measured in a considerably larger momentum range than in the previous experiments.     

The use of quasielastic pion-proton backward scattering at 0.7 GeV/c for studying Fermi motion in light nuclei

The plane-wave approximation was used to examine the proton Fermi-momentum distribution in experiments on quasielastic large-momentum-transfer pion-nucleon scattering in light nuclei ⁶Li, ⁷Li, and ¹²C. It was found that, unlike the (e, e′) reaction, the Fermi-gas model is in poor agreement with experiment, whereas the oscillator model adequately describes the spectrum shape. However, the parameters obtained for these distributions are sizably smaller than those derived from the (e, e′)) experiments. This suggests that the plane-wave approach is inadequate and that more complicated theoretical approaches, supposedly allowing for pion-nucleon amplitude modification in nuclear matter, are necessary for the analysis of experimental data.     

Manifestation of quark clusters in the emission of cumulative protons in the experiment on the fragmentation of carbon ions

The proton yields at an angle of 3.5° have been measured in the FRAGM experiment on the fragmentation of carbon ions with the energies T ₀ = 0.6, 0.95, and 2.0 GeV/nucleon on a beryllium target at the heavy-ion accelerator complex TWAC (terawatt accumulator, Institute for Theoretical and Experimental Physics). The data are represented in the form of the dependences of the invariant cross section for proton yield on the cumulative variable x in the range of 0.9 < x < 2.4. This invariant cross section varies within six orders of magnitude. The proton spectra have been analyzed within the theoretical approach of the fragmentation of quark clusters with the fragmentation functions obtained in the quark-gluon string model. The probabilities of the existence of six- and nine-quark clusters in the carbon nuclei are estimated as 8–12 and 0.2–0.6%, respectively. The results are compared to the estimated of quark effects obtained by other methods.