Measurements of spin rotation parameter A in pion-proton elastic scattering at 1.62 GeV/c

The ITEP-PNPI collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at P_beam = 1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared to the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.Comment: 7 pages, 3 figures. To be published in Phys. Lett.

Membranes with a boundary

We investigate the recently developed theory of multiple membranes. In particular, we consider open membranes, i.e. the theory defined on a membrane world volume with a boundary. We first restrict our attention to the gauge sector of the theory. We obtain a boundary action from the Chern-Simons terms. Secondly, we consider the addition of certain boundary terms to various Chern-Simons theories coupled to matter. These terms ensure the full bulk plus boundary action has the correct amount of supersymmetry. For the ABJM model, this construction motivates the inclusion of a boundary quartic scalar potential. The boundary dynamics obtained from our modified theory produce Basu-Harvey type equations describing membranes ending on a fivebrane. The ultimate goal of this work is to throw light on the theory of fivebranes using the theory of open membranes.Comment: 48 pages, Latex, v2 references adde

Simulation of Spatial Correlation of Polarization Characteristics for Meteor Radio Reflections

The paper relates to a spatial correlation of polarization characteristics of radio waves scattered from ionized meteor trails. The accurate modeling of polarization of meteor radio reflections is achieved through a separate consideration of oblique diffraction on meteor trails of both the longitudinal and the transverse components of the electric field of incident radio waves. The Faraday polarization twist due to propagation in the ionosphere is also taken into account. By a computer simulation of two typical meteor radio links, we assess a correlation between the polarizations of the radio reflections received at two separate antennas spaced at various distances and along various azimuth directions. It is shown that, in some cases, a coherence radius of the polarization characteristics may exceed 100 km, and its main limiting factor is an inhomogeneity of scattering properties along the meteor trail. The obtained spatial correlation curves are crucial for assessing secrecy of the shared encryption keys generated from the measurements of random polarizations of meteor radio reflections. Our estimates reveal a certain vulnerability of the polarization-based key generation systems to the channel eavesdropping

Analysis of Polarization Diversity Applicability in Meteor Key Distribution Systems

Natural randomness of meteor-scatter channel can be used for establishing a shared encryption key. In order to improve the key generation rate, a new method is proposed that allows sampling two independent measurements of carrier phase from each meteor radio reflection. The method relies on a time multiplexing of polarization of probing signals. Using a computer simulation based on numerical calculations of oblique diffraction of radio waves on ionized meteor trails, estimates of polarization coherence interval of the meteor-scatter channel are performed. Correlation functions of carrier phase versus polarization diversity of the probing signals are obtained both for the cases of horizontally and vertically polarized antennas. It is shown that, theoretically, use of the proposed polarization diversity technique provides a twice higher key generation rate compared to previous studies. On the other hand, the proposed method demands a very precise tuning of antenna polarization, which may be difficult for a practical implementation

Calculation of Total Electron Content for Simulation of Meteor-Scatter Radio Links

© 2020 IEEE. Channel nonreciprocity is one of understudied features of meteor-scatter radio propagation that is caused mainly by polarization phenomena in the channel. For correct estimation of the nonreciprocity level, accurate values of the Faraday polarization twist are required that leads to problem of calculation of Total Electron Content of the ionosphere (TEC) along the signal propagation path. In this paper, the TEC is calculated by direct numerical integration of the ionosphere electron density throughout uplink to a meteor trail. The calculation method is based on division of the uplink path into several segments, each characterized by its own electron density height profile. Our computations made for 10000 various meteor trails simulated for a typical meteor radio link of 720-km length showed quite unambiguously that precise integration along the propagation path can be replaced with high accuracy by simple integration over the single electron height profile containing the signal reflection point. Estimates of the difference between the TEC values calculated for the opposite propagation uplink paths to meteor trail from both link ends are presented. It is shown that these differences are tiny and can be neglected at modeling meteor-scatter links

Simulation of periodic synchronization of UAV's clock

Unmanned aerial vehicles (UAVs) is one of the most fast progressing technologies. High space-time flexibility of UAV networks along with the ability to payload sensitive measuring equipment allows establishing aerial wireless sensor networks (AWSNs) with new qualities. However, establishing a rapidly reconfigurable phased antenna array system for precise spatially distributed measurements requires a high-quality frequency-phase synchronization of the AWSN drones. Particularly, this paper relates to the problem of designing a synchronized AWSN with a centralized architecture. By a computer simulation, we assess an accuracy of the periodic synchronization of two crystal oscillators installed at the AWSN drones as onboard clocks. Two synchronization methods are considered: based on the total phase of a single carrier frequency and based on the differential phase of two carrier frequencies. It is shown that for most practical tasks it is sufficient to transmit a synchronizing signal with a period ranging from 1 to 20 seconds. The corresponding synchronization error of two onboard clocks can be held under 1.5 ns in the case of using of OCXO-oscillators and under 10.5 ns when using TCXO-oscillators, respectively

Simulation of short-term instability of UAV's clock

Unmanned aerial vehicles (UAVs) is one of the most fast progressing technologies. High space-time flexibility of UAV networks along with the ability to payload sensitive measuring equipment allows establishing aerial wireless sensor networks (AWSNs) with new qualities. However, establishing a rapidly reconfigurable phased antenna array system for precise spatially distributed measurements requires a high-quality frequency-phase synchronization of the AWSN drones. In particular, this paper relates to the problem of designing a synchronized AWSN with a centralized architecture. A model for simulating random frequency offset of two TCXO or OCXO crystal oscillators used as onboard frequency standards installed at the AWSN drones is presented. Our simulation results show that under continuous real-time synchronization, the synchronization error of the master and slave drones can be held under 1.5 ns for at least 100-second intervals

Predictability Assess of Multipath Phase Using ARIMA Model

© 2020 IEEE. Physical Layer Security is a promising technique for establishing a secret encryption key in wireless communications. The secret key is distilled from the Channel State Information under conditions of its random fast fading. However, random channel variations are quite smooth on short-term intervals and can be predicted using previous samples. This is a serious threat to secrecy of the generated encryption key. In this study, we assess both prediction error and prediction horizon for real data set of a fast fading carrier phase using the ARIMA model. Influence of the autoregressive model order on the prediction accuracy is considered, optimum ARIMA parameters for forecasting the experimental data are found. We also compare prediction accuracy of the ARIMA that uses fixed model parameters versus accuracy of the auto-ARIMA that employs adaptive estimation of model parameters in different timeframes of the data. Our results showed that effective prediction of real samples of multipath phase was possible only at intervals shorter than 150 ms, and maximum prediction gain did not exceed 40 degrees compared to prediction based on the last known sample