712 research outputs found
Theory of muonic hydrogen - muonic deuterium isotope shift
We calculate the corrections of orders alpha^3, alpha^4 and alpha^5 to the
Lamb shift of the 1S and 2S energy levels of muonic hydrogen (mu p) and muonic
deuterium (mu d). The nuclear structure effects are taken into account in terms
of the proton r_p and deuteron r_d charge radii for the one-photon interaction
and by means of the proton and deuteron electromagnetic form factors in the
case of one-loop amplitudes. The obtained numerical value of the isotope shift
(mu d) - (mu p) for the splitting (1S-2S) 101003.3495 meV can be considered as
a reliable estimation for corresponding experiment with the accuracy 10^{-6}.
The fine structure interval E(1S)-8E(2S) in muonic hydrogen and muonic
deuterium are calculated.Comment: 22 pages, 7 figure
Relativistic effects in the processes of heavy quark fragmentation
In the framework based on the quasipotential method and relativistic quark
model a new covariant expression for the heavy quark fragmentation amplitude to
fragment into the pseudoscalar and vector S-wave heavy mesons is obtained. It
contains all possible relativistic corrections including the terms connected
with the transformation law of the bound state wave function to the reference
frame of the moving meson. Relativistic corrections of order {\bf p}^2/m^2 to
the heavy quark fragmentation distributions into (\bar c c), (\bar b c) and
(\bar b b) states are calculated as functions of the longitudinal momentum
fraction z and the transverse momentum p_T relative to the jet axis.Comment: 23 pages, 6 figure
Hyperfine Structure of S-States in Muonic Helium Ion
Corrections of orders alpha^5 and alpha^6 are calculated in the hyperfine
splittings of 1S and 2S - energy levels in the ion of muonic helium. The
electron vacuum polarization effects, the nuclear structure corrections and
recoil corrections are taken into account. The obtained numerical values of the
hyperfine splittings -1334.56 meV (1S state), -166.62 meV (2S state) can be
considered as a reliable estimate for the comparison with the future
experimental data. The hyperfine splitting interval Delta_{12}=(8 Delta
E^{hfs}(2S)- Delta E^{hfs}(1S)) = 1.64 meV can be used for the check of quantum
electrodynamics.Comment: 14 pages, 5 figure
Nuclear structure corrections in the energy spectra of electronic and muonic deuterium
The one-loop nuclear structure corrections of order (Z alpha)^5 to the Lamb
shift and hyperfine splitting of the deuterium are calculated. The contribution
of the deuteron structure effects to the isotope shift (ep)-(ed), (mu p)-(mu d)
in the interval (1S - 2S) is obtained on the basis of modern experimental data
on the deuteron electromagnetic form factors. The comparison with the similar
contributions to the Lamb shift for electronic and muonic hydrogen shows, that
the relative contribution due to the nucleus structure increases when passing
from the hydrogen to the deuterium.Comment: Talk presented at the Conference "Physics of Fundamental
Interactions" of the Nuclear Physics Section of the Physics Department of
RAS, ITEP, Moscow, 2-6 December, 2002; 8 pages, REVTE
Thermal radiation of conducting nanoparticles
The thermal radiation of small conducting particles was investigated in the
region where the Stephan-Boltzmann law is not valid and strongly overestimates
radiation losses. The new criterion for the particle size, at which black body
radiation law fails, was formulated. The approach is based on the magnetic
particle polarization, which is valid until very small sizes (cluster size)
where due to drop of particle conductivity the electric polarization prevails
over the magnetic one. It was also shown that the radiation power of clusters,
estimated on the basis of the experimental data, is lower than that given by
the Stephan-Boltzmann law.Comment: 12 pages, 5 figures, 1 tabl
Muonic hydrogen ground state hyperfine splitting
Corrections of orders alpha^5, alpha^6 are calculated in the hyperfine
splitting of the muonic hydrogen ground state. The nuclear structure effects
are taken into account in the one- and two-loop Feynman amplitudes by means of
the proton electromagnetic form factors. The modification of the hyperfine
splitting part of the Breit potential due to the electron vacuum polarization
is considered. Total numerical value of the 1S state hyperfine splitting
182.638 meV in the (mu p) can play the role of proper estimation for the
corresponding experiment with the accuracy 30 ppm.Comment: 18 pages, Talk presented at the 11th Lomonosov Conference on
Elementary Particle Physics, Moscow State University, August 200
Improved Estimates of Biomass Expansion Factors for Russian Forests
Biomass structure is an important feature of terrestrial vegetation. The parameters of forest biomass structure are important for forest monitoring, biomass modelling and the optimal utilization and management of forests. In this paper, we used the most comprehensive database of sample plots available to build a set of multi-dimensional regression models that describe the proportion of different live biomass fractions (i.e., the stem, branches, foliage, roots) of forest stands as a function of average stand age, density (relative stocking) and site quality for forests of the major tree species of northern Eurasia. Bootstrapping was used to determine the accuracy of the estimates and also provides the associated uncertainties in these estimates. The species-specific mean percentage errors were then calculated between the sample plot data and the model estimates, resulting in overall relative errors in the regression model of −0.6%, −1.0% and 11.6% for biomass conversion and expansion factor (BCEF), biomass expansion factor (BEF), and root-to-shoot ratio respectively. The equations were then applied to data obtained from the Russian State Forest Register (SFR) and a map of forest cover to produce spatially distributed estimators of biomass conversion and expansion factors and root-to-shoot ratios for Russian forests. The equations and the resulting maps can be used to convert growing stock volume to the components of both above-ground and below-ground live biomass. The new live biomass conversion factors can be used in different applications, in particular to substitute those that are currently used by Russia in national reporting to the UNFCCC (United Nations Framework Convention on Climate Change) and the FAO FRA (Food and Agriculture Organization’s Forest Resource Assessment), among others
Bryophyte Diversity of Calcareous Fens in the Bashkir Cis-Urals (Republic of Bashkortostan, the Southern Urals)
The bryophyte diversity of base-rich fens was studied in 16 calcareous mires of the Bashkir Cis-Urals (the Southern Ural region). Thirty-seven moss species and nine liverworts were recorded in treeless communities dominated by Schoenus ferrugineus, Molinia caerulea, small sedges and mosses. The annotated species list with precise locations is provided. Most of the surveyed mires are located in the northeastern part of the Bashkir Cis-Urals, that is, in the Mesyagutovo forest-steppe bordering with the western foothills of the Southern Ural Mountains. In the plain areas of the western part of the Bashkir Cis-Urals, calcareous mires are very rare and characterized by the low number of habitat specialists. Arctic-boreo-alpine species (Cinclidium stygium,Paludella squarrosa, Palustriella decipiens, Pseudocalliergon trifarium, etc.) make up approximately 30% of the total bryophyte diversity of the surveyed fens. In the study area, these species grow in small isolated populations at the southern limit of the species range. Currently, only half of the surveyed calcareous mires are located within protected areas. It is essential to improve the protection of these unique habitats inthe study area.
Keywords: calcareous mires, base-rich fens, bryophytes, the Southern Ural
Fine and hyperfine structure of the muonic ^3He ion
On the basis of quasipotential approach to the bound state problem in QED we
calculate the vacuum polarization, relativistic, recoil, structure corrections
of orders and to the fine structure interval and to the hyperfine structure of the energy
levels and in muonic ion. The resulting values
, , provide reliable
guidelines in performing a comparison with the relevant experimental data.Comment: 15 pages, 4 figures, 3 table
Evaluation of the self-energy correction to the g-factor of S states in H-like ions
A detailed description of the numerical procedure is presented for the
evaluation of the one-loop self-energy correction to the -factor of an
electron in the and states in H-like ions to all orders in .Comment: Final version, December 30, 200
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