Estimations of electron-positron pair production at high-intensity laser interaction with high-Z targets

Electron-positron pairs' generation occuring in the interaction of $10^{18}$-$10^{20}$~W/cm$^2$ laser radiation with high-Z targets are examined. Computational results are presented for the pair production and the positron yield from the target with allowance for the contribution of pair production processes due to electrons and bremsstrahlung photons. Monte-Carlo simulations using the PRIZMA code confirm the estimates obtained. The possible positron yield from high-Z targets irradiated by picosecond lasers of power $10^2$-$10^3$~TW is estimated to be $10^9$-$10^{11}$

Formation of 24Mg* in the Splitting of 28Si Nuclei by 1-GeV Protons

The 28Si(p, p' gamma)24Mg reaction has been studied at the ITEP accelerator by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two reaction products are detected: a 1368.6-keV gamma-ray photon accompanying the transition of the 24Mg* nucleus from the first excited state to the ground state and a proton p' whose momentum is measured in a magnetic spectrometer. The measured distribution in the energy lost by the proton in interaction is attributed to five processes: the direct knockout of a nuclear alpha cluster, the knockout of four nucleons with a total charge number of 2, the formation of the DeltaSi isobaric nucleus, the formation of the Delta isobar in the interaction of the incident proton with a nuclear nucleon, and the production of a pi meson, which is at rest in the nuclear reference frame. The last process likely corresponds to the reaction of the formation of a deeply bound pion state in the 28P nucleus. Such states were previously observed only on heavy nuclei. The cross sections for the listed processes have been estimated.Comment: 14 pages, 3 figures submitted to JETP Letter

Examination of the astrophysical S-factors of the radiative proton capture on 2H, 6Li, 7Li, 12C and 13C

Astrophysical S-factors of radiative capture reactions on light nuclei have been calculated in a two-cluster potential model, taking into account the separation of orbital states by the use of Young schemes. The local two-body potentials describing the interaction of the clusters were determined by fitting scattering data and properties of bound states. The many-body character of the problem is approximatively accounted for by Pauli forbidden states. An important feature of the approach is the consideration of the dependence of the interaction potential between the clusters on the orbital Young schemes, which determine the permutation symmetry of the nucleon system. Proton capture on 2H, 6Li, 7Li, 12C, and 13C was analyzed in this approach. Experimental data at low energies were described reasonably well when the phase shifts for cluster-cluster scattering, extracted from precise data, were used. This shows that decreasing the experimental error on differential elastic scattering cross sections of light nuclei at astrophysical energies is very important also to allow a more accurate phase shift analysis. A future increase in precision will allow more definite conclusions regarding the reaction mechanisms and astrophysical conditions of thermonuclear reactions.Comment: 40p., 9 fig., 83 ref. arXiv admin note: substantial text overlap with arXiv:1005.1794, arXiv:1112.1760, arXiv:1005.198

In memoriam two distinguished participants of the Bregenz Symmetries in Science Symposia: Marcos Moshinsky and Yurii Fedorovich Smirnov

Some particular facets of the numerous works by Marcos Moshinsky and Yurii Fedorovich Smirnov are presented in these notes. The accent is put on some of the common interests of Yurii and Marcos in physics, theoretical chemistry, and mathematical physics. These notes also contain some more personal memories of Yurii Smirnov.Comment: Submitted for publication in Journal of Physics: Conference Serie

Microscopics of meson degrees of freedom in nucleons and mesons in nuclei - what can be seen in the process of quasielastic knockout of mesons by high-energy electrons

Developed earlier concept of quasielastic knock out of pions from nucleons by high-energy electrons is propounded as a tool for checking microscopical model ($^3P_0$ - fluctuation) for decay of N to different channels $\pi+B$ and Preparata model of nucleus structure.Comment: 6 pages, 5 figures, Talk given at 16 Baldin Symposium in June 200

Astrophysical S-factor of 4He12C radiative capture at low energies

The possibility to describe the astrophysical S-factor of the 4He12C radiative capture is considered in the potential cluster model at the energy range 0.1-4.0 MeV. It is shown that the approach used, which takes into account E2 transitions only, gives a good description of the new experimental data for adjusted parameters of potentials and leads to the value S(300) = 16.0$\cdotp$keV b.Comment: 8 Pag

Astrophysical S-factor for the radiative capture reaction 13C(p,g)14N

The phase shift analysis, done on the basis of the known measurements of the differential cross-sections of the p13C elastic scattering at the energy range 250-750 keV, shows that it is enough to take into account only 3S1 wave in the considered energy region. The potential for the triplet 3S1 state in p13C system at the resonance energy 0.55 MeV corresponding to quantum numbers JpT = 1-1 as well as the potential for the 3P1 bound state of 14N were constructed on the basis of the obtained scattering phase shifts. The possibility to describe the experimental data of the astrophysical S-factor of the p13C radiative capture at the energies 0.03-0.8 MeV was considered within the potential cluster model with the forbidden states. It was shown that we properly succeed in explanation of the energy behavior of the astrophysical S-factor for the p13C radiative capture at the resonance energy range 0.55 MeV (laboratory system).Comment: 8 p., 2 fi

Deuteron And Alpha-Particle Total Reaction Cross Sections For Nuclei With A~50

The total reaction cross sections for the target nuclei 45 Sc, 48 Ti, 51 V and 52,53,54 Cr induced by 13.6 MeV deuterons and 27.2 MeV alpha particles were measured. The deuteron-induced total reaction cross sections for 48 Ti and 52,54 Cr are well reproduced by optical-model calculations. Ambiguity of parameters for these nuclei is reduced considerably. The total reaction cross sections corresponding to alpha particles are analysed in the quasiclassical approximation. It is shown that isotopic-isotonic effects may be explained quantitatively if one assumes that the diffuseness of the nuclear density distribution for the nucleus 52 Cr is less than that for 51 V by Delta a=0.28+or-0.11 fm, and the diffuseness of the isotope 54 Cr is greater than that for 52 Cr by Delta a=0.13+or-0.11 fm. The optical-model analysis of elastic scattering and total reaction cross sections for the nuclei 45 Sc, 48 Ti and 51 V was carried out concurrently. The experimental data are explained successfully using a six-parameter optical potential