12 research outputs found

    Mass of the higgs versus fourth generation masses

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    The predicted value of the higgs mass mHm_H is analyzed assuming the existence of the fourth generation of leptons (N,EN, E) and quarks (U,DU, D). The steep and flat directions are found in the five-dimensional parameter space: mHm_H, mUm_U, mDm_D, mNm_N, mEm_E. The LEPTOP fit of the precision electroweak data is compatible (in particular) with mH300m_H \sim 300 GeV, mN50m_N \sim 50 GeV, mE100m_E \sim 100 GeV, mU+mD500m_U +m_D \sim 500 GeV, and mUmD75|m_U -m_D| \sim 75 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

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    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

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    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

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    Nowadays in the MSSM the moderate values of tanβ\tan\beta 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 mh125m_h\sim 125 GeV at values of tanβ1.9\tan\beta\ge 1.9. In the investigated model the lightest Higgs boson mass does not exceed 130.5±3.5130.5\pm 3.5 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

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    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 94±5GeV94\pm 5\text{GeV}. 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 mh125GeVm_h\sim 125\text{GeV} even for comparatively low values of tanβ1.9\tan\beta\ge 1.9. 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 130.5±3.5GeV130.5\pm 3.5\text{GeV}.Comment: 34 pages, 5 figures included, LaTeX 2

    Enhanced electroweak radiative corrections in SUSY and precision data

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    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

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    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 WW-boson mass mWm_W and to ZZ l+ll^+ l^- coupling constants. The comparison with the result of the Standard Model fit is made
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