Analytical evaluation of certain on-shell two-loop three-point diagrams

An analytical approach is applied to the calculation of some dimensionally-regulated two-loop vertex diagrams with essential on-shell singularities. Such diagrams are important for the evaluation of QED corrections to the muon decay, QCD corrections to top quark decays t->W^{+}b, t->H^{+}b, etc.Comment: 2 pages, LaTeX, contribution to proceedings of ACAT2002 (Moscow, June 2002

Spin-resonance modes of the spin-gap magnet TlCuCl_3

Three kinds of magnetic resonance signals were detected in crystals of the spin-gap magnet TlCuCl_3. First, we have observed the microwave absorption due to the excitation of the transitions between the singlet ground state and the excited triplet states. This mode has the linear frequency-field dependence corresponding to the previously known value of the zero-field spin-gap of 156 GHz and to the closing of spin-gap at the magnetic field H_c of about 50 kOe. Second, the thermally activated resonance absorption due to the transitions between the spin sublevels of the triplet excitations was found. These sublevels are split by the crystal field and external magnetic field. Finally, we have observed antiferromagnetic resonance absorption in the field-induced antiferromagnetic phase above the critical field H_c. This resonance frequency is strongly anisotropic with respect to the direction of the magnetic field.Comment: v.2: typo correction (one of the field directions was misprinted in the v.1

NIR Microscopy Possibilities for the Visualization of Silicon Microelectronic Structure Topology through the Substrate

AbstractExperimental setup based on visible and NIR spectral range microscope with laser port and picosecond laser is developed for silicon integrated circuit (IC) failure analysis. The possibility of visualizing the topology of the submicron technology silicon structures from the back side of the crystal through the substrate is shown. Main features of new setup are demonstrated by some results of backside focused pulsed laser beam initiated latchup effect study. The possibility of the localization of the latchup sensitive areas under focused laser irradiation is shown. NIR light emission accompanying the latchup effect is observed and analyzed. The practical aspects of NIR microscopy for failure analysis under backside laser irradiation are discussed

P-matrix and J-matrix approaches. Coulomb asymptotics in the harmonic oscillator representation of scattering theory

The relation between the R- and P-matrix approaches and the harmonic oscillator representation of the quantum scattering theory (J-matrix method) is discussed. We construct a discrete analogue of the P-matrix that is shown to be equivalent to the usual P-matrix in the quasiclassical limit. A definition of the natural channel radius is introduced. As a result, it is shown to be possible to use well-developed technique of R- and P-matrix theory for calculation of resonant states characteristics, scattering phase shifts, etc., in the approaches based on harmonic oscillator expansions, e.g., in nuclear shell-model calculations. P-matrix is used also for formulation of the method of treating Coulomb asymptotics in the scattering theory in oscillator representation.Comment: Revtex, 57 pages including 15 figures; to be published in Annals of Physic

Microwave resonator probe diagnoctics of plasma density fluctuations

The unique diagnostics of the low frequency waves excited in magnetoplasma was tested on large “Krot” device. Method is based on measuring the resonance curve frequency and amplitude modulation of a tiny double-wire probe caused by plasma density variations. Depending on the operating point position at the probe resonance characteristic we can measure density fluctuations down to δn/n ≤ 10⁻⁵. The possibility of harmonic and non-periodic density perturbation measurements is shown in experiments. We also demonstrate the possibility of using the resonator probe as a noninvasive medical tool to diagnose the pathologies and diseases accompanied by changes in tissue complex dielectric coefficient.На експериментальному стенді «Крот» реалізована оригінальна діагностика амплітуди низькочастотних хвиль, порушуваних у замагніченій плазмі. Метод заснований на вимірі частоти й амплітуди модуляції резонансної частоти мініатюрного дротового резонатора, що викликаються флуктуацією густини плазми. Виміряються флуктуації густини порядку δn/n ≤ 10⁻⁵. Продемонстровано можливість застосування резонансної системи для діагностики не тільки плазми, але і довільних діелектричних середовищ без порушення їхньої цілісності. Аналізуються такі питання, як глибина зондування, можливість визначення просторових і електродинамічних характеристик неоднорідностей. Демонструється можливість застосування методики в медицині.На експериментальному стенді «Крот» реалізована оригінальна діагностика амплітуди низькочастотних хвиль, порушуваних у замагніченій плазмі. Метод заснований на вимірі частоти й амплітуди модуляції резонансної частоти мініатюрного дротового резонатора, що викликаються флуктуацією густини плазми. Виміряються флуктуації густини порядку δn/n ≤ 10⁻⁵. Продемонстровано можливість застосування резонансної системи для діагностики не тільки плазми, але і довільних діелектричних середовищ без порушення їхньої цілісності. Аналізуються такі питання, як глибина зондування, можливість визначення просторових і електродинамічних характеристик неоднорідностей. Демонструється можливість застосування методики в медицині

Small-threshold behaviour of two-loop self-energy diagrams: some special cases

An algorithm to construct analytic approximations to two-loop diagrams describing their behaviour at small non-zero thresholds is discussed. For some special cases (involving two different-scale mass parameters), several terms of the expansion are obtained.Comment: 7 pages, plain latex; talk given at DESY-Zeuthen Workshop "QCD and QED in Higher Order", Rheinsberg, April 1996, to appear in Proceeding

Investigation of thermal and magnetic properties of defects in a spin-gap compound NaV2O5

The specific heat, magnetic susceptibility and ESR signals of a Na-deficient vanadate Na_xV_2O_5 (x=1.00 - 0.90) were studied in the temperature range 0.07 - 10 K, well below the transition point to a spin-gap state. The contribution of defects provided by sodium vacancies to the specific heat was observed. It has a low temperature part which does not tend to zero till at least 0.3 K and a high temperature power-like tail appears above 2 K. Such dependence may correspond to the existence of local modes and correlations between defects in V-O layers. The magnetic measurements and ESR data reveal S=1/2 degrees of freedom for the defects, with their effective number increasing in temperature and under magnetic field. The latter results in the nonsaturating magnetization at low temperature. No long-range magnetic ordering in the system of defects was found. A model for the defects based on electron jumps near vacancies is proposed to explain the observed effects. The concept of a frustrated two-dimensional correlated magnet induced by the defects is considered to be responsible for the absence of magnetic ordering.Comment: 6 pages, 8 figure

Electromagnetic Neutrino Properties and Neutrino Oscillations in Electromagnetic Fields

The presence of medium and external magnetic field change electromagnetic properties of neutrino. In this article the behavior of neutrino magnetic moment in electromagnetic field is considered. On the basis the Bargmann-Michel-Telegdi equation for the case of models with CP invariance and P nonconservation the new type of neutrino resonances $\nu_L \leftrightarrow \nu_R$ in the electromagnetic field is predicted.Comment: 6 page