Landau-Pomeranchuk-Migdal effect for finite-size targets

A rigorous evaluation of the Landau-Pomeranchuk-Migdal effect for finite-size targets is performed within the path integral approach previously developed by the author [B. G. Zakharov, JETP Lett. 63, 952 (1996)]. The bremsstrahlung rate in QED is expressed through a solution of a two-dimensional Schrödinger equation with an imaginary potential. The boundary condition for this solution is formulated in terms of a product of the light-cone electron-photon wave function and the dipole cross section for scattering of an e ⁺ e ^? pair off an atom. Numerical calculations are performed for homogeneous and structured targets. Our predictions for the homogeneous target agree well with the photon spectrum measured recently at SLAC with 25-GeV electrons. The spectra obtained for the structured, two-segment targets exhibit interference minima and maxima.     

A Big Horizontal Solar Telescope of the Main Astronomical Observatory of the Ukrainian National Academy of Sciences in the caucasus

This paper presents the Big Horizonal Solar Telescope of the Main Astronomical Observatory of the Ukrainian National Academy of Sciences installed at the Peak Terskol high-altitude station near Elbrus (the main mirror diameter is 650 mm and the focal length is 17.5 m). The telescope is equipped with a five-camera spectrograph intended for photographic spectral observations of active regions in the solar atmosphere and photoelectric measurements of the solar spectra with high spectral and spatial resolution. The observation procedure is described, and the results of the quality analysis of the recorded spectra and of the early measurements are presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1326–1333, October, 1996.The authors wish to express their gratitude to C.I.Gandzha, V.V.Kul'beda, and Yu. M. Gavrilyuk from the Solar Physics Department of the PAO of the Ukrainian NAS and to the Board of Directors of the Observatory and of the High-Altitude Station for help in the development of the instrument.This paper is dedicated to the memory of E. A. Gurtovenko, D.Sc. in Phys. and Math., who initiated the installation of the telescope at Peak Terskol and who was the leader, an executor, and an observer in this project.     

On a multiplicative function on the set of shifted primes

It is proved that if ?(n) is a multiplicative function taking a valueζ on the set of primes such thatζ ³ = 1,ζ ≠ 1 and? ³(p ^r)=1 forr≥2, then there exists aθ ∈ (0, 1), for which $$|\sum\limits_{p \leqslant x} f (p + 1)| \leqslant \theta \pi (x)$$ , where $$\pi (x) = \sum\limits_{p \leqslant x} 1$$ .     

On the location parameter confidence intervals based on a random size sample from a partially known population

The problem of constructing confidence intervals of a fixed length for the location parameter based on a random size sample is considered. It is proposed to use the confidence interval $$\theta _p^* - u\sqrt p /\sigma< \theta< \theta _p^* + u\sqrt p /\sigma $$ , whereθ _p ^* is an adaptive estimator,σ ² is the Fisher information, and p^?1 is the mean of the sample size. Nonparametric bounds are given for the limit as p → 0 confidence probability. Bibliography: 5 titles.     

Nonfactorization and the decaysD s +→φπ +,φρ + andφl + ν l

Using the experimentally measured values ofx=A ₂(0)/A ₁(0) andy=V(0)/A ₁(0) and the measured ratiosR _st=Γ(D _s ⁺ →φl ⁺ ν _l)/Γ(D _ins ⁺ →φπ ⁺) andR _h=Γ(D _s ⁺ →φρ ⁺)/Γ(D _s ⁺ →φπ ⁺), we present evidence for significant nonfactorization contribution in the decay amplitude forD _s ⁺ →φπ ⁺. We analyze the role of nonfactorization inD _s ⁺ →φρ ⁺ and conclude that present data onR _h are consistent with factorization inD _s ⁺ →φρ ⁺. A measurement of polarization inD _s ⁺ →φρ ⁺ would greatly assist our analysis.     

1H NMR study on the inclusion of bicyclo[3.3.1]nonanes in cyclodextrins

- and -cyclodextrins were found to form 1:1 inclusion complexes with 2,6- and 2,9-substituted bicyclo[3.3.1]nonanes. The binding constants and the structure of the complexes were estimated from titration studies and 2D ROESY experiments.     

Microwave sputtering of conductors and insulators for optical emission and mass spectrometry

A microwave-powered slab-line cavity was used to excite a discharge in low pressure argon or neon and to demonstrate the sputtering of conducting and non-conducting samples by a microwave excited discharge. Both optical emission spectroscopy and mass spectrometry were used as detection systems. The dependence of the signals on gas pressure and net microwave power was investigated.