151 research outputs found
Yang-Mills theory in (2+1) dimensions: a short review
The analysis of (2+1)-dimensional Yang-Mills ( theory via the use
of gauge-invariant matrix variables is reviewed. The vacuum wavefunction,
string tension, the propagator mass for gluons, its relation to the magnetic
mass for at nonzero temperature and the extension of our analysis to
the Yang-Mills-Chern-Simons theory are discussed.Comment: 14 pages, Talk at Lightcone Workshop, Trento, 2001, to appear in
Nucl.Phys.(Proc.
The Values of and Derived from the Non-Observation of Electroweak Radiative Corrections at LEP: Global Fit
A set of equations representing the mass ratio and various observables
of decays in terms of , , ,
, , , and (all
other fermion masses being neglected) are compared with the latest data of the
four LEP detectors, which at the level of one standard deviation coincide with
their Born values. Our global fit gives: , where the central values
correspond to GeV, the first errors are statistical and the second
ones represent shifts of the central values corresponding to
GeV() and 60 GeV(). The predicted mass of the top is smaller than in the
recent fits by 4 GeV. The {\it predicted} values of and the LEP
observables, based on the fitted values of and , show a
weak dependence on and differ by several {\it predicted} standard
deviations from the corresponding Born values. The uncertainties of the
predicted values and their deviations from the corresponding Born values
determine the experimental accuracy required to observe electroweak radiative
corrections.Comment: LaTex, 15 pages (including 3 figures as EPS files at the end
Gauge invariant variables and the Yang-Mills-Chern-Simons theory
A Hamiltonian analysis of Yang-Mills (YM) theory in (2+1) dimensions with a
level Chern-Simons term is carried out using a gauge invariant matrix
parametrization of the potentials. The gauge boson states are constructed and
the contribution of the dynamical mass gap to the gauge boson mass is obtained.
Long distance properties of vacuum expectation values are related to a
Euclidean two-dimensional YM theory coupled to flavors of Dirac fermions in
the fundamental representation. We also discuss the expectation value of the
Wilson loop operator and give a comparison with previous results.Comment: 20 pages, Plain Te
Axial vector current in an electromagnetic field and low-energy neutrino-photon interactions
An expression for the axial vector current in a strong, slowly varying
electromagnetic field is obtained. We apply this expression to the construction
of the effective action for low-energy neutrino-photon interactions.Comment: 6 pages, references updated, final version to appear in Phys. Rev.
A gauge-invariant Hamiltonian analysis for non-Abelian gauge theories in (2+1) dimensions
The Hamiltonian formulation for a non-Abelian gauge theory in two spatial
dimensions is carried out in terms of a gauge-invariant matrix parametrization
of the fields. The Jacobian for the relevant transformation of variables is
given in terms of the WZW-action for a hermitian matrix field. Some
gauge-invariant eigenstates of the kinetic term of the Hamiltonian are given;
these have zero charge and exhibit a mass gap.Comment: 22 pages, Plain TeX, modifications in sections 3 and 4 to include
change of regularization. (This version will be published in Nucl.Phys.B
Influence of small miscuts on self-ordered growth of Ge nanoislands
Using high-resolution X-ray diffraction (HRXRD), we have investigated
lateral ordering the nanoislands formed from Ge wetting layer of various thicknesses
deposited on a strained Si₁₋xGex sublayer. We observed that the high lateral ordering
degree is initiated by ordered modulation of non-uniform deformation fields. This
modulation is induced by small (∼0.3°) misorientation of Si substrate from [001]
direction. Finally, we show that the miscut can be the source of perfectly ordered
nanoisland arrays in two dimensions when the growth is performed on the strained SiGe
(001) sublayer. The effect of substrate miscut can be amplified tuning the deviation of
buffer layer surface from [001] growth direction via increasing the Ge content
Extraction of Kaon Formfactors from K^- -> mu^- nu_mu gamma Decay at ISTRA+ Setup
The radiative decay K->mu nu gamma has been studied at ISTRA+ setup in a new
kinematical region. About 22K events of K^- -> mu^- nu_mu gamma have been
observed. The sign and value of Fv-Fa have been measured for the first time.
The result is Fv-Fa=0.21(4)(4).Comment: 11 pages, 21 figures, submitted to Phys. Lett.
Search for light pseudoscalar sgoldstino in K- decays
A search for the light pseudoscalar sgoldstino production in the three body
K- decay K-->pipi0P has been performed with the ISTRA+ detector exposed to the
25 GeV negative secondary beam of the U70 proton synchrotron. No signal is
seen. An upper limit for the branching ratio Br(K->pipi0P), at 90% confidence
level, is found to be around 9*10**-6 in the effective mass m(P) range from 0
till 200 MeV, excluding the region near m(pi0) where it degrades to 3.5*10**-5.Comment: 10 pages, LATEX, 8 EPS figures, revised version, to be published in
Phys.Lett.
High statistic measurement of the K- -> pi0 e- nu decay form-factors
The decay K- -> pi0 e- nu is studied using in-flight decays detected with the
ISTRA+ spectrometer. About 920K events are collected for the analysis. The
lambda+ slope parameter of the decay form-factor f+(t) in the linear
approximation (average slope) is measured: lambda+(lin)= 0.02774 +-
0.00047(stat) +- 0.00032(syst). The quadratic contribution to the form-factor
was estimated to be lambda'+ = 0.00084 +- 0.00027(stat) +- 0.00031(syst). The
linear slope, which has a meaning of df+(t)/dt|_{t=0} for this fit, is lambda+
= 0.02324 +- 0.00152(stat) +- 0.00032(syst). The limits on possible tensor and
scalar couplings are derived: f_{T}/f_{+}(0)=-0.012 +- 0.021(stat) +-
0.011$(syst), f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).Comment: 11 pages, 8 figures. Accepted by Phys.Lett.
Search for Heavy Neutrino in K->mu nu_h(nu_h-> nu gamma) Decay at ISTRA+ Setup
Heavy neutrino nu_h with m_h < 300MeV/c^2 can be effectively searched for in
kaon decays. We put upper limits on mixing matrix element |U_mu_h}|^2 for
radiatively decaying nu_h from K->mu nu_h (nu_h -> nu gamma) decay chain in the
following parameter region: 30MeV/c^2 < m_h < 80MeV/c^2; 10^{-11}sec < tau_h <
10^{-9}sec. For the whole region |U_{mu h}|^2 < 5 x 10^{-5} for Majorana type
of nu_h and | U_{\mu h}|^2 < 8 x 10^{-5} for the Dirac case.Comment: Published in Phys. Lett.
- …