1,164 research outputs found
Effects of Ground-State Correlations on High Energy Scattering off Nuclei: the Case of the Total Neutron-Nucleus Cross Section
With the aim at quantitatively investigating the longstanding problem
concerning the effect of short range nucleon-nucleon correlations on scattering
processes at high energies, the total neutron-nucleus cross section is
calculated within a parameter-free approach which, for the first time, takes
into account, simultaneously, central, spin, isospin and tensor nucleon-nucleon
(NN) correlations, and Glauber elastic and Gribov inelastic shadowing
corrections. Nuclei ranging from 4He to 208Pb and incident neutron momenta in
the range 3 GeV/c - 300 GeV/c are considered; the commonly used approach which
approximates the square of the nuclear wave function by a product of one-body
densities is carefully analyzed, showing that NN correlations can play a
non-negligible role in high energy scattering off nuclei.Comment: 5 pages, 3 figure
Electromagnetic Structure of the Meson in the Light-Front Quark Model
We investigate the elastic form factors of the rho meson in the light-front
quark model(LFQM). With the phenomenologically accessible meson vertices
including the one obtained by the Melosh transformation frequently used in the
LFQM, we find that only the helicity matrix element of the plus
current receives the zero-mode contribution. We quantify the zero-mode
contribution in the helicity amplitude using the angular condition of
spin-1 system. After taking care of the zero-mode issue, we obtain the
magnetic() and quadrupole() moments of the rho meson as and
, respectively, in the LFQM consistent with the Melosh transformation
and compare our results with other available theoretical predictions.Comment: 14pages, 5figure
Number of Collisions in the Glauber Model and Beyond
The so called number of hadron-nucleus collisions n_coll(b) at impact
parameter b, and its integral value N_coll, which are used to normalize the
measured fractional cross section of a hard process, are calculated within the
Glauber-Gribov theory including the effects of nucleon short-range
correlations. The Gribov inelastic shadowing corrections are summed to all
orders by employing the dipole representation. Numerical calculations are
performed at the energies of the BNL Relativistic Heavy Ion Collider (RHIC) and
CERN Large Hadron Collider (LHC). We found that whereas the Gribov corrections
generally increase the value of N_coll, the inclusion of nucleon correlations,
acting in the opposite directions, decreases it by a comparable amount. The
interplay of the two effects varies with the value of the impact parameter.Comment: Text expanded; typos corrected; results and conclusions unchanged. To
appear in Phys. Rev.
Uakitite, VN, a new mononitride mineral from uakit iron meteorite (IIAB)
Uakitite was observed in small troilite–daubréelite (±schreibersite) inclusions (up to 100 µm) and in large troilite–daubréelite nodules (up to 1 cm) in Fe-Ni-metal (kamacite) of the Uakit iron meteorite (IIAB), Republic of Buryatia, Russia. Such associations in the Uakit meteorite seemed to form due to high-temperature (>1000 °C) separation of Fe-Cr-rich sulfide liquid from Fe-metal melt. Most inclusions represent alternation of layers of troilite and daubréelite, which may be a result of solid decay of an initial Fe-Cr-sulfide. These inclusions are partially resorbed and mainly located in fissures of the meteorite, which is now filled with magnetite, and rarely other secondary minerals. Phase relations indicate that uakitite is one of the early minerals in these associations. It forms isometric (cubic) crystals (in daubréelite) or rounded grains (in schreibersite). The size of uakitite grains is usually less than 5 µm. It is associated with sulfides (daubréelite, troilite, grokhovskyite), schreibersite and magnetite. Carlsbergite CrN, a more abundant nitride in the Uakit meteorite, was not found in any assemblages with uakitite. Physical and optical properties of uakitite are quite similar to synthetic VN: yellow and transparent phase with metallic luster; Mohs hardness: 9–10; light gray color with a pinky tint in reflected light; density (calc.) = 6.128 g/cm3. Uakitite is structurally related to the osbornite group minerals: carlsbergite CrN and osbornite TiN. Structural data were obtained for three uakitite crystals using the electron backscatter diffraction (EBSD) technique. Fitting of the EBSD patterns for a synthetic VN model (cubic, Fm-3m, a = 4.1328(3) Å; V = 70.588(9) Å3; Z = 4) resulted in the parameter MAD = 0.14–0.37° (best-good fit). Analytical data for uakitite (n = 54, in wt. %) are: V, 71.33; Cr, 5.58; Fe, 1.56; N, 21.41; Ti, below detection limit (<0.005). The empirical formula (V0.91Cr0.07Fe0.02)1.00N1.00 indicates that chromium incorporates in the structure according to the scheme V3+ → Cr3+ (up to 7 mol. % of the carlsbergite end-member). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, RFBR: 17-05-00129, IGM SD 0330-2016-0005Government Council on Grants, Russian FederationMinistry of Science and Higher Education of the Russian FederationFunding: The investigations were partly supported by RFBR (grant 17-05-00129) and the State assignment project (IGM SD 0330-2016-0005). This work was also supported by the Initiative Project of Ministry of Science and Higher Education of the Russian Federation and by Act 211 of the Government of the Russian Federation, agreement no. 02.A03.21.0006
The main problems of building the system of statistical indicators in the field of cryonics
Cryonics as rather inconsistent, but constantly developing sphere of activity of modern society cannot be adequately estimated by means of separate private indicators or even their enlarged groups. This requires the development of a system of indicators that includes not only the traditional parameters of material and technical base and human capacity, but also the scale, intensity, results and consequences of cryonic activities. The key problems of the system of indicators of critical activity statistics, its features and possible approaches to its construction have been considered in the article
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