2,818 research outputs found
Photons and static gravity
The influence of static gravitational field on frequency, wave-length and
velocity of photons and on the energy levels of atoms and nuclei is considered
in the most elementary way. The interconnection between these phenomena is
stressed.Comment: LaTeX, 9 pages, no figures, the end of section 5 is modifie
The controllability function method
The paper is devoted to the control problem for the movement of an overhead crane with the use of a dynamic model in the form of "trolley - cargo" mechanical system and the driving force as a control parameter. To solve the system of differential equations, which describe the movement of the system taking into account constraints for the control, the controllability function method is applied. The algorithm for solving the problem is described, a program is developed as well as difficulties, which occur while implementing the method, and ways of its solution are marked. Results of constructing the control and system trajectories are also provided as an example of the program work
Testing Parity with Atomic Radiative Capture of
The next generation of "intensity frontier" facilities will bring a
significant increase in the intensity of sub-relativistic beams of . We
show that the use of these beams in combination with thin targets of
elements opens up the possibility of testing parity-violating interactions of
muons with nuclei via direct radiative capture of muons into atomic 2S
orbitals. Since atomic capture preserves longitudinal muon polarization, the
measurement of the gamma ray angular asymmetry in the single photon
- transition will offer a direct test of parity. We
calculate the probability of atomic radiative capture taking into account the
finite size of the nucleus to show that this process can dominate over the
usual muonic atom cascade, and that the as yet unobserved single photon
- transition in muonic atoms can be detected in this way
using current muon facilities.Comment: To appear in PR
Do Present LEP Data Provide Evidence for Electroweak Corrections?
The Born approximation, based on instead of
, reproduces all electroweak precision measurements within their
accuracy. The low upper limits for the genuinely electroweak
corrections constitute one of the major achievements of LEP. The astonishing
smallness of these corrections results from the cancellation of a large
positive contribution from the heavy top quark and large negative contributions
from all other virtual particles. It is precisely the non-observation of
electroweak radiative corrections that places stringent upper and lower limits
on the top mass.Comment: 12 pages, preprint CERN-TH.6943/9
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
Baryogenesis in Cosmological Model with Superstring-Inspired E_6 Unification
We have developed a concept of parallel existence of the ordinary (O) and
hidden (H) worlds with a superstring-inspired E_6 unification, broken at the
early stage of the Universe into SO(10) X U(1) - in the O-world, and SU(6)' X
SU(2)' - in the H-world. As a result, we have obtained in the hidden world the
low energy symmetry group G'_SM X SU(2)'_\theta, instead of the Standard Model
group G_SM. The additional non-Abelian SU(2)'_\theta group with massless gauge
fields, "thetons", is responsible for the dark energy. We present a
baryogenesis mechanism with the B-L asymmetry produced by the conversion of
ordinary leptons into particles of the hidden sector.Comment: 15 pages, 2 figure
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
Multi-lepton Signatures of a Hidden Sector in Rare B Decays
We explore the sensitivity of flavour changing b -> s transitions to a
(sub-)GeV hidden sector with generic couplings to the Standard Model through
the Higgs, vector and axion portals. The underlying two-body decays of B
mesons, B -> X_s S and B0 -> SS, where S denotes a generic new GeV-scale
particle, may significantly enhance the yield of monochromatic lepton pairs in
the final state via prompt decays of S to a dilepton pair. Existing
measurements of the charged lepton spectrum in neutral-current semileptonic B
decays provide bounds on the parameters of the light sector that are
significantly more stringent than the requirements of naturalness. New search
modes, such as B -> X_s + n(l+l-) and B0 -> n(l+l-) with n > 1 can provide
additional sensitivity to scenarios in which both the Higgs and vector portals
are active, and are accessible to (super-)B factories and hadron colliders.Comment: 12 pages, 2 figures; v2: reference added, minor correction
CP violation in unpolarized e^+ e^- to charginos at one loop level
We study CP violation in e^+ e^- to \tilde\chi_i^+\tilde\chi_j^- in the
framework of the MSSM. Though the cross section of this process is CP-even at
the tree level even for polarized electron-positron beams, we show that it
contains a CP-odd part at the one loop order and there are CP-odd observables
that can in principle be measured even using unpolarized electron-positron
beams. The relevant diagram calculations are briefly discussed and the results
of selected (box) diagram computations are shown.Comment: similar to Phys. Rev. D version, but corrected figs. 4, 5, 6 (factor
four
- …