12 research outputs found
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
Анализ источников тока на операционных усилителях, согласно требований их прецизионности в широкой полосе частот для задач электроимпедансной томографии
В роботі розглянуті особливості функціонування двох класичних схем джерел струму в ЕІТ, — операційний підсилювач з навантаженням (досліджуваним об’єктом) у колі зворотного зв’язку, та схеми Хауленда в широкій смузі частот. В кожній зі схем використаний ОП та негативний ЗЗ за струмом для збільшення вихідного опору цих джерел. Приведені відповідні аналітичні залежності струму навантаження від частоти для обох джерел. Надані практичні рекомендації при виборі ОП для таких схем,згідно вимог їх прецизійності в широкій смузі частот.Introduction. The typical approaches for the current sources designing are considered. The difficulties of providing their precision in a wide frequency range are formulated. The necessary requirements for their precision in a wide frequency range are also specified.
Formulation of the problem. The most of existing current sources are implemented using operational amplifiers. It is shown by short review of them. Such solutions do not fully provide the requirements of precision in their work in a wide frequency range. The possibility of using operational amplifiers is analyzed; the limits of their application are determined. The research methods and the analysis of results. The load current on the frequency an-alytical dependencies for these schemes were calculated and critically analyzed. The results are illustrated on the graphs. The ratios for practical recommendations for such schemes de-signing are calculated. Conclusions. The arguments for inexpediency of operational amplifiers application for schemes of current sources in all frequency range are presented. The operational amplifiers with a greater bandwidth should be used for large load resistance values. The other elements of the electrical circuits (namely transconductance amplifiers) using is proposed.В работе рассмотрены особенности функционирования двух классических схем источников тока для электоимпедансной томографии, - операционный усилитель с нагрузкой в цепи обратной связи и схема Хауленда в широкой полосе частот. В каждой из схем использован операционный усилитель и отрицательная обратная связь по току для увеличения выходного сопротивления этих схем. Приведены соответствующие аналитические зависимости тока нагрузки от частоты для обоих источников. Даны практические рекомендации при выборе операционных усилителей для таких схем, учитывая требования к прецизионности в широкой полосе частот
Neutrino magnetic moments and low-energy solar neutrino-electron scattering experiments
The scattering of solar neutrinos on electrons is sensitive to the neutrino
magnetic moments through an interference of electromagnetic and weak amplitudes
in the cross section. We show that future low-energy solar neutrino experiments
with good angular resolution can be sensitive to the resulting azimuthal
asymmetries in event number and should provide useful information on
non-standard neutrino properties such as magnetic moments. We compare
asymmetries expected at HELLAZ (mainly pp neutrinos) with those at the
Kamiokande and Super-Kamiokande experiments (Boron neutrinos), both for the
case of Dirac and Majorana neutrinos and discuss the advantages of low
energies. Potentially interesting information on the solar magnetic fields may
be accessible.Comment: 21 pages, latex, 5 PS figures, uses revtex, text improved, to be
published in Phys. Rev.
Higgs bosons in the simplest SUSY models
Nowadays in the MSSM the moderate values of are almost excluded
by LEP II lower bound on the lightest Higgs boson mass. In the Next-to-Minimal
Supersymmetric Standard Model the theoretical upper bound on it increases and
reaches maximal value in the strong Yukawa coupling limit when all solutions of
renormalization group equations are concentrated near the quasi-fixed point.
For calculation of Higgs boson spectrum the perturbation theory method can be
applied. We investigate the particle spectrum in the framework of the modified
NMSSM which leads to the self-consistent solution in the strong Yukawa coupling
limit. This model allows one to get GeV at values of
. In the investigated model the lightest Higgs boson mass
does not exceed GeV. The upper bound on the lightest CP-even
Higgs boson mass in more complicated supersymmetric models is also discussed.Comment: 27 pages, 5 figures included, LaTeX 2e. Plenary talk at the
Conference of RAS Nuclear Physics Department 2000 in ITEP, Moscow, Russia; to
appear in Phys. Atom. Nuc
Particle spectrum in the modified NMSSM in the strong Yukawa coupling limit
A theoretical analysis of solutions of renormalisation group equations in the
MSSM corresponding to the quasi-fixed point conditions shows that the mass of
the lightest Higgs boson in this case does not exceed . It
means that a substantial part of the parameter space of the MSSM is practically
excluded by existing experimental data from LEP II. In the NMSSM the upper
bound on the lightest Higgs boson mass reaches its maximum in the strong Yukawa
coupling regime, when Yukawa constants are considerably larger the gauge ones
on the Grand Unification scale. In this paper a particle spectrum in a simple
modification of NMSSM which leads to a self-consistent solution in the
considered region of the parameter space is studied. This model allows one to
get even for comparatively low values of . For an analysis of the Higgs boson spectrum and neutralino spectrum a
method for diagonalisation of mass matrices proposed formerly is used. The mass
of the lightest Higgs boson in this model does not exceed .Comment: 34 pages, 5 figures included, LaTeX 2
Enhanced electroweak radiative corrections in SUSY and precision data
Enhanced radiative corrections generated in SUSY extensions of the Standard Model spoil the fit of the precision data (Z-boson decay parameters and W-boson mass). This negative effect is washed out for heavy enough squarks, because of the decoupling property of SUSY models. We find that even for light squarks the enhanced radiative corrections can be small. In this case substantial ˜tL ˜tR mixing is necessary. 1 A number of predictions of the Standard Model are now tested with an accuracy of the order of 0.1%. There are two (more or less) free parameters in the Standard Model: the value of the strong coupling constant ˆαs(mZ) and the mass of the Higgs boson mH. Making a fit of the latest set of precision data reported in [1] (Z-boson decay parameters, W-boson and top-quark masses), we obtain: mH = (71 +8
Enhanced electroweak radiative corrections in SUSY: gluon-free observables
Large top quark mass is responsible for the enhancement of the oblique radiative corrections in SUSY models. We present the analytical formulas for these corrections to the -boson mass and to coupling constants. The comparison with the result of the Standard Model fit is made