Hypernuclei as chiral solitons

The identification of flavored multiskyrmions with the ground states of known hypernuclei is successful for several of them, e.g. for isodoublet H(Lambda) - He(Lambda), A=4, isoscalars He(Lambda) (A=5) and Li(Lambda) (A=7). In other cases agreement is not so good, but the behaviour of the binding energy with increasing baryon number is in qualitative agreement with data. Charmed or beauty hypernuclei within this approach are predicted to be bound stronger than strange hypernuclei. This conclusion is stable against variation of poorly known heavy flavor decay constants.Comment: 9 pages, 1 Fig. Presented at the International Workshops on Nuclear and Particle Physics at 50-Gev PS, NP01 (KEK, Japan, December 2001) and NP02 (Kyoto, Japan, September 2002). Some additions and corrections of numerical results are mad

On Tamm's problem in the Vavilov-Cherenkov radiation theory

We analyse the well-known Tamm problem treating the charge motion on a finite space interval with the velocity exceeding light velocity in medium. By comparing Tamm's formulae with the exact ones we prove that former do not properly describe Cherenkov radiation terms. We also investigate Tamm's formula cos(theta)=1/(beta n) defining the position of maximum of the field strengths Fourier components for the infinite uniform motion of a charge. Numerical analysis of the Fourier components of field strengths shows that they have a pronounced maximum at cos(theta)=1/(beta n) only for the charge motion on the infinitely small interval. As the latter grows, many maxima appear. For the charge motion on an infinite interval there is infinite number of maxima of the same amplitude. The quantum analysis of Tamm's formula leads to the same results.Comment: 28 pages, 8 figures, to be published in J.Phys.D:Appl.Phy

Fine structure of Vavilov-Cherenkov radiation near the Cherenkov threshold

We analyze the Vavilov-Cherenkov radiation (VCR) in a dispersive nontransparent dielectric air-like medium both below and above the Cherenkov threshold, in the framework of classical electrodynamics. It is shown that the transition to the subthreshold energies leads to the destruction of electromagnetic shock waves and to the sharp reduction of the frequency domain where VCR is emitted. The fine wake-like structure of the Vavilov-Cherenkov radiation survives and manifests the existence of the subthreshold radiation in the domain of anomalous dispersion. These domains can approximately be defined by the two phenomenological parameters of the medium, namely, the effective frequency of oscillators and the damping describing an interaction with the other degrees of freedom.Comment: 9 pages, 6 figure

Determination of the b quark mass at the M_Z scale with the DELPHI detector at LEP

An experimental study of the normalized three-jet rate of b quark events with respect to light quarks events (light= \ell \equiv u,d,s) has been performed using the CAMBRIDGE and DURHAM jet algorithms. The data used were collected by the DELPHI experiment at LEP on the Z peak from 1994 to 2000. The results are found to agree with theoretical predictions treating mass corrections at next-to-leading order. Measurements of the b quark mass have also been performed for both the b pole mass: M_b and the b running mass: m_b(M_Z). Data are found to be better described when using the running mass. The measurement yields: m_b(M_Z) = 2.85 +/- 0.18 (stat) +/- 0.13 (exp) +/- 0.19 (had) +/- 0.12 (theo) GeV/c^2 for the CAMBRIDGE algorithm. This result is the most precise measurement of the b mass derived from a high energy process. When compared to other b mass determinations by experiments at lower energy scales, this value agrees with the prediction of Quantum Chromodynamics for the energy evolution of the running mass. The mass measurement is equivalent to a test of the flavour independence of the strong coupling constant with an accuracy of 7 permil.Comment: 24 pages, 10 figures, Accepted by Eur. Phys. J.

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.

A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events

Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.

Synthesis of a Filter of Phase-Domanipulated Signals with a Minimum Side-Lobe Level

В статье показана возможность обнаружения воздушных объектов с помощью макета кластера радиолокационной станции вертикального зондирования (РЛС ВЗ) с проведением натурных испытаний и оценкой достижимых характеристик обнаружения. В макете в качестве зондирующего сигнала применялся 13-элементный код Баркера. Принятый сигнал сжимается в согласованном фильтре приемного устройства, в результате чего вокруг основного отклика формируются боковые лепестки. Количество боковых лепестков N – 1, где N – число дискрет ФКМ‑сигнала. Боковые лепестки имеют одинаковую амплитуду и треугольную форму, а их уровень в N раз меньше уровня основного отклика [1, 2]. Наличие боковых лепестков нежелательно по причине возможного маскирования сигнала, отраженного от цели с малой эффективной площадью рассеяния (ЭПР), боковыми лепестками сигналов, отраженных от цели с большой ЭПР, что зачастую наблюдается в зоне отражений от местных предметов. Таким образом, существует риск, что цель с малой ЭПР не будет обнаружена приемником. Кроме того, боковые лепестки вносят вклад в увеличение уровня шумов при обнаружении цели в области отражений от местных предметов, гидрометеообразований и т.п. Учитывая это, в макете для значительного уменьшения уровня боковых лепестков было разработано и применено устройство подавления боковых лепестков (УПБЛ) с использованием инверсных фильтров [3]. В предлагаемом УПБЛ используется обратная фильтрация с помощью цифровых фильтров, благодаря чему боковые лепестки сжатого в приемнике радиолокационного импульса теоретически могут быть полностью устранены, а в практическом случае происходит значительное подавление боковых лепестковThe article shows the possibility of detecting airborne objects using a model of a vertical sounding radar cluster (VZ radar) with field tests and an assessment of the achievable detection characteristics. In the layout, a 13-element Barker code was used as a probing signal. The received signal is compressed in the receiver’s matched filter, resulting in sidelobes around the main response. The number of side lobes is N – 1, where N is the number of discretes of the PCM signal. The side lobes have the same amplitude and triangular shape, and their level is N times less than the level of the main response [1, 2]. The presence of side lobes is undesirable due to the possible masking of a signal reflected from a target with a small effective scattering area (ESR) by side lobes of signals reflected from a target with a large ESR, which is often observed in the area of reflections from local objects. Thus, there is a risk that a target with a low RCS will not be detected by the receiver. In addition, side lobes contribute to an increase in the noise level when a target is detected in the area of reflections from local objects, hydrometeorological formations, etc. With this in mind, in the layout, to significantly reduce the level of side lobes, a side-lobe suppression device (SBSL) was developed and used using inverse filters [3]. The proposed UPBL uses inverse filtering with digital filters, due to which the side lobes of the radar pulse compressed in the receiver can theoretically be completely eliminated, and in the practical case there is a significant suppression of the side lobe

Study of Leading Hadrons in Gluon and Quark Fragmentation

The study of quark jets in e+e- reactions at LEP has demonstrated that the hadronisation process is reproduced well by the Lund string model. However, our understanding of gluon fragmentation is less complete. In this study enriched quark and gluon jet samples of different purities are selected in three-jet events from hadronic decays of the Z collected by the DELPHI experiment in the LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are defined by requiring a rapidity gap and their sum of charges is studied. An excess of leading systems with total charge zero is found for gluon jets in all cases, when compared to Monte Carlo Simulations with JETSET (with and without Bose-Einstein correlations included) and ARIADNE. The corresponding leading systems of quark jets do not exhibit such an excess. The influence of the gap size and of the gluon purity on the effect is studied and a concentration of the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is observed, indicating that gluon jets might have an additional hitherto undetected fragmentation mode via a two-gluon system. This could be an indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.