3,635 research outputs found
High-power radiating plasma
The physical principles underlying the use of radiating plasmas for the optical pumping of lasers are described. Particular consideration is given to the properties of radiating plasmas; radiation selectivity; the dynamics, equilibrium, and stability of radiating plasmas; the radiative Reynolds number; and experimental results on radiating discharges
Theory of Z boson decays
The precision data on Z boson decays from LEP-I and SLC colliders are
compared with the predictions based on the Minimal Standard Theory. The Born
approximation of the theory is based on three most accurately known
observables: G_mu -- the four fermion coupling constant of muon decay, m_Z --
the mass of the Z boson, and alpha(m_Z) -- the value of the running fine
structure constant at the scale of m_Z. The electroweak loop corrections are
expressed, in addition, in terms of the masses of higgs, m_H, of the top and
bottom quarks, m_t and m_b, and of the strong interaction constant
alpha_s(m_Z). The main emphasis of the review is focused on the
one-electroweak-loop approximation. Two electroweak loops have been calculated
in the literature only partly. Possible manifestations of new physics are
briefly discussed.Comment: 80 pages, 16 figures, accepted in Reports on Progress in Physic
Electroweak radiative corrections in Z boson decays
Contribution to A.D.Sakharov memorial volume. A detailed review of the
electroweak radiative corrections to the Z-boson decays in the framework of the
Minimal Standard Modelm (MSM) is presented. After a short historical
introduction we describe the optimal parametrization of the MSM, especially of
the Born approximation, and derive expressions for the one-loop electroweak
corrections. Finally a global fit of all relevant experimental data is
performed, resulting in fitted values of the top-quark mass, m_t, and strong
coupling constant /alpha_s. Allowed range for the value of the Higgs mass, m_H,
is discussed. Various details of calculations are described in 16 appendices.Comment: 98 pages,21 EPS and PS figures,uses epsf.sty, separate file with the
tared, compressed and uuencoded figures is awailable at
http://wwwtheor.itep.ru/~vysotsky/figures.u
On the search for 50 GeV neutrinos
Using the computer code CompHEP we estimate the number of events and the
background, at LEP II and TESLA, for the reaction ,
where is a hypothetical Dirac neutrino with mass of the order of 50 GeV.Comment: Standard LaTeX, 9 pages, 2 tables, 3 figure
Precision measurements, extra generations and heavy neutrino
The existence of extra chiral generations with all fermions heavier than
is strongly disfavored by the precision electroweak data. The exclusion
of one additional generation of heavy fermions in SUSY extension of Standard
Model is less forbidden if chargino and neutralino have low degenerate masses
with GeV. However the data are fitted nicely even by a few
extra generations, if one allows neutral leptons to have masses close to 50
GeV. Such heavy neutrino can be searched in the reaction at LEP-200 with total final luminosity of .Comment: 5 pages, 6 figures, Proceedings ICHEP2000 Osaka conferenc
Nonlinear acoustic waves in channels with variable cross sections
The point symmetry group is studied for the generalized Webster-type equation
describing non-linear acoustic waves in lossy channels with variable cross
sections. It is shown that, for certain types of cross section profiles, the
admitted symmetry group is extended and the invariant solutions corresponding
to these profiles are obtained. Approximate analytic solutions to the
generalized Webster equation are derived for channels with smoothly varying
cross sections and arbitrary initial conditions.Comment: Revtex4, 10 pages, 2 figure. This is an enlarged contribution to
Acoustical Physics, 2012, v.58, No.3, p.269-276 with modest stylistic
corrections introduced mainly in the Introduction and References. Several
typos were also correcte
Mass of the higgs versus fourth generation masses
The predicted value of the higgs mass is analyzed assuming the
existence of the fourth generation of leptons () and quarks ().
The steep and flat directions are found in the five-dimensional parameter
space: , , , , . The LEPTOP fit of the precision
electroweak data is compatible (in particular) with GeV, GeV, GeV, GeV, and GeV. The quality of fits drastically improves when the data on b- and
c-quark asymmetries and new NuTeV data on deep inelastic scattering are
ignored.Comment: 8 pages, 4 figure
Evidence of Microfossils in Carbonaceous Chondrites
Investigations have been carried out on freshly broken, internal surfaces of the Murchison, Efremovka and Orgueil carbonaceous chondrites using Scanning Electron Microscopes (SEM) in Russia and the Environmental Scanning Electron Microscope (ESEM) in the United States. These independent studies on different samples of the meteorites have resulted in the detection of numerous spherical and ellipsoidal bodies (some with spikes) similar to the forms of uncertain biogenicity that were designated "organized elements" by prior researchers. We have also encountered numerous complex biomorphic microstructures in these carbonaceous chondrites. Many of these complex bodies exhibit diverse characteristics reminiscent of microfossils of cyanobacteria such as we have investigated in ancient phosphorites and high carbon rocks (e.g. oil shales). Energy Dispersive Spectroscopy (EDS) analysis and 2D elemental maps shows enhanced carbon content in the bodies superimposed upon the elemental distributions characteristic of the chondritic matrix. The size, distribution, composition, and indications of cell walls, reproductive and life cycle developmental stages of these bodies are strongly suggestive of biology' These bodies appear to be mineralized and embedded within the meteorite matrix, and can not be attributed to recent surface contamination effects. Consequently, we have interpreted these in-situ microstructures to represent the lithified remains of prokaryotes and filamentous cyanobacteria. We also detected in Orgueil microstructures morphologically similar to fibrous kerite crystals. We present images of many biomorphic microstructures and possible microfossils found in the Murchison, Efremovka, and Orgueil chondrites and compare these forms with known microfossils from the Cambrian phosphate-rich rocks (phosphorites) of Khubsugul, Northern Mongolia
Volkov solution for two laser beams and ITER
We find the solution of the Dirac equation for two plane waves (laser beams)
and we determine the modified Compton formula for the scattering of two photons
on an alectron. The practical meaning of the two laser beams is, that two laser
beams impinging on a targed which is constituted from material in the form of a
foam, can replace 100-200 laser beams impinging on a normal targed. It means
that the nuclear fusion with two laser beams is realistic in combination with
the nuclear reactor such as ITER.Comment: 13 page
Non-perturbative vacuum-polarization effects in proton-laser collisions
In the collision of a high-energy proton beam and a strong laser field,
merging of the laser photons can occur due to the polarization of vacuum. The
probability of photon merging is calculated by accounting exactly for the laser
field and presents a highly non-perturbative dependence on the laser intensity
and frequency. It is shown that the non-perturbative vacuum-polarization
effects can be experimentally measured by combining the next-generation of
table-top petawatt lasers with presently available proton accelerators.Comment: 5 pages, 2 figure
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