2,221 research outputs found
Couplings of heavy hadrons with soft pions from QCD sum rules
We estimate the couplings in the Heavy Hadron Chiral Theory (HHCT) lagrangian
from the QCD sum rules in an external axial field. We take into account the
perturbative correction to the meson correlator in the infinite mass limit.
With the perturbative correction and three successive power corrections, the
meson correlator in an axial field becomes one of the best known correlators.
In spite of this, the corresponding sum rule is not very stable. It yields the
result g_1 F^2/(380MeV)^3 = 0.1 - 0.2, where F^2 = f_M^2 m/4 = (380MeV)^3 is
the central value of the heavy meson decay constant with the perturbative
correction. This result is surprisingly low as compared with the constituent
quark model estimate g_1 = 0.75. The sum rules for g_{2,3} following from
nondiagonal Sigma-Sigma and diagonal Lambda-Sigma baryon correlators in an
external axial field suggest g_{2,3} = 0.4 - 0.7, while diagonal Sigma-Sigma
and nondiagonal Lambda-Sigma baryon sum rules have too large uncertainties.Comment: 15 pages, LaTeX2e, 6 ps figures include
Sudy of the Propagation of Decimeter Radiowaves in the Atmosphere of Venus with the Aid of AIS ''venera 4''
Radio wave propagation in Venus atmosphere based on approximating inhomogeneity of refractivit
Geochemical aspect of impact cratering: Studies in Vernadsky Institute
Studies of the geochemical effects of impact cratering at the Vernadsky Institute in collaboration with the Institute of Dynamics of Geospheres, Moscow State University, Leningrad State University, and some other institutions were fulfilled by several approaches. At the initial stage, three approaches were used: (1) experimental studies of high-temperature vaporization of geological materials (basalts, granites, and so on) in vacuum that was considered as a model of behavior of impact melt and vapor; (2) search of impact-induced geochemical effects in the rock from terrestrial impact craters; and (3) studies of samples of lunar regolith. The next stage of the studies included experiments on quasi-equilibrium vaporization of geological material in Knudsen cells. The results of this investigation are discussed
On the Possible Common Nature of Double Extensive Air Showers and Aligned Events
Double Extensive Air Showers and aligned events were discovered at energies E
{\gtsim} 1016 eV over fourth century back. But up to now there is no
sufficiently identical explanation of their nature. In this paper it is
expected that both types of events are the result of breakup of the string
formed in the collisions of super high energy particles
Coulomb tunneling for fusion reactions in dense matter: Path integral Monte Carlo versus mean field
We compare Path Integral Monte Carlo calculations by Militzer and Pollock
(Phys. Rev. B 71, 134303, 2005) of Coulomb tunneling in nuclear reactions in
dense matter to semiclassical calculations assuming WKB Coulomb barrier
penetration through the radial mean-field potential. We find a very good
agreement of two approaches at temperatures higher than ~1/5 of the ion plasma
temperature. We obtain a simple parameterization of the mean field potential
and of the respective reaction rates. We analyze Gamow-peak energies of
reacting ions in various reaction regimes and discuss theoretical uncertainties
of nuclear reaction rates taking carbon burning in dense stellar matter as an
example.Comment: 13 pages, 7 figures, to appear in Phys. Rev.
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