On the choice of the lateral distribution function for EAS charged particles

Knowledge of the lateral distribution function (LDF) of charged particles in extensive air showers (EASs) is necessary for adequate determination of both the total number N _e of particles and other parameters used to classify the showers selected for analysis. Many researchers continue to actively use the Nishimura-Kamata-Greisen LDF despite that fact that it was obtained theoretically within a fairly rough approximation of electromagnetic cascade theory. In this study, the dependence of the shape of the EAS spectrum over the number of particles on the type of LDF used to treat experimental data is investigated. The Nishimura-Kamata-Greisen function and the scaling function are analyzed [5]. Major attention is given to the data obtained at the Moscow State University EAS array.     

Lateral distribution of EAS muons measured for the primary cosmic ray energy around 100 TeV

The muonic component of the extensive air showers (EAS) is of great importance for the astroparticle physics. It carries the information about the properties of primary cosmic ray (CR) particles, such as their mass, and electromagnetic and hadronic nature. It provides a sensitive test for the hadronic interaction models, which are inevitable for describing the cascade shower development of cosmic rays in EAS experiments. The YangBaJing Hybrid Array (YBJ-HA) experiment has been in operation since the end of 2016. Surface detectors are used for the measurements of primary energy, angular direction and core position of a shower event, while underground muon detectors are used for measuring the density of muons at various locations. Using the data obtained by the YBJ-HA experiment,this work reports the first measurement of the lateral muon distribution for the primary cosmic ray energy in the 100TeV region. The punch-through effect is evaluated via MC simulation.     

Lateral distribution function of charged particles in EAS near the axis

High-precision measurements of the lateral distribution function (LDF) of charged particles near the axis of extensive air showers (EASes) were performed with the CARPET air shower array of the Baksan Neutrino Observatory for several ranges of N _e , including the knee region. For the sake of comparison with the experiment, calculations for primary protons and iron nuclei were made using the CORSIKA code (the QGSJET01C model of interaction). The measured experimental LDF is compared with our calculations.     

Spatial distribution of EAS radio emission at 32 MHz

The results of the reprocessing of the experimental data on radio emission from extensive air showers (EAS) earlier obtained at the EAS facility (Moscow State University) are reported. The maximum depth distribution of showers is found from analysis of the width of the spatial distribution of radio emission. The average maximum depth is X _max = 655 ± 8 g/cm² for the primary particle energy E ₀ ～ (3–4) × 10¹⁷ eV. The normalized field strength at E ₀ = 10¹⁷ eV is 3.2 ± 0.6 and 2.8 ± 0.4 μV/(m MHz) at distances of 50 and 100 m from the axis, respectively. The accuracy of E ₀ determination from the radio emission field strength at 50 m from the axis is about 20%.     

Substructures in the temporal distribution of atmospheric ?erenkov light in EAS

Summary Substructures have been observed in the arrival time distribution of the atmospheric Čerenkov light in extensive air showers. The arrival time can be related to a position in the shower plane, indicating the existence of density variations,i.e. substructures in the lateral distribution of particles. The frequency of substructures is a few %, core distances up to tens of metres have been observed.

---

Riassunto Nella distribuzione temporale della luce Čerenkov associata agli sciami estesi atmosferici sono state osservate molteplicità su tempi Δt≈(1÷10) ns. Questo tempo può essere correlato ad una definita posizione nel piano dello sciame, indicando così l'esistenza di variazioni di densità anomale, e quindi di sottostrutture, nella distribuzione laterale degli elettroni. La frequenza di tali anomalie è ≈1%, esse sono state osservate fino a distanze di alcune decine di metri dall'asse dell'EAS.

---

Резюме В широких атмосферных ливнях наблюдаются субструктуры в распределении времен прихода атмосферного черенковского излучения. Время прихода может быть связано с положением плоскости ливня, указывая на существование изменений плотности, т.е. субструктур в поперечном распределении частиц. Частота субструктур составляет несколько процентов, наблюдаются расстояния между центрами вплоть до десятков метров.

     

SS-HORSE method for studying resonances

A new method for analyzing resonance states based on the Harmonic-Oscillator Representation of Scattering Equations (HORSE) formalism and analytic properties of partial-wave scattering amplitudes is proposed. The method is tested by applying it to the model problem of neutral-particle scattering and can be used to study resonance states on the basis of microscopic calculations performed within various versions of the shell model.     

A new method for observing the shower cascade profile at the Yakutsk EAS array

An empirical approach is presented for reconstruction of the extensive air shower (EAS) cascade curve according to data of the Cherenkov track detector. The proposed method, unlike conventional ones, is based on experimentally measured parameters and on calculated values which weakly depend on the model of shower development.     

A biomagnetic method for studying gastro-intestinal activity

Summary A novel method to investigate the gastro-intestinal activity by means of a superconducting instrumentation based on SQUID sensors developed for biomagnetic measurements is presented. The magnetic field generated by a small marker ingested by the subject is measured over the abdomen. The localization of the marker,i.e. a magnetic dipole, is carried out by means of a standard algorithm used in biomagnetic studies. In this way it is possible to noninvasively study the activity of the gastro-intestinal system. This new approach may lead to important clinical applications.     

Underground hadronic calorimeter for EAS studies

An innovative method for studying the properties of extensive air showers (EASes) that is based on the detection of thermal neutrons generated by high energy hadrons under a soil absorber of 500 g cm⁻² is proposed and tested. It is shown that underground hadronic calorimeter can be performed with special scintillation detectors developed by the authors. The method could be quite useful in gamma shower selection and investigations of EAS properties, primary cosmic ray mass composition, EAS core location, and so on.     

用局部常化三倍角公式研究单摆周期

应用局部常化方法对三倍角公式进行局部常化处理,对一类非线性动力学方程进行了一种简洁的近似修正,得到精确度较高的大摆角单摆运动周期的两个新结论,同时用此结论推导出一个简洁的推论,并且用3种方法进行了具体比较.     

New multiple histogram method for studying phase transitions

For temperature zero the effects of disorder for interacting bosons are considered. The disorder induced superfluid-insulator transition in thed-dimensional disordered Bogoliubov model is discussed. Results for a short-range and a long-range random potential are given. For short-range disorder we argue that ford<4 arbitrarily small disorder localizes the Bose condensate for vanishing interaction potential. Ford>4 a certain strength of the disorder potential is necessary in order to localize the condensate. For the three-dimensional Bogoliubov model our results are in agreement with a recent calculation. We compare our theoretical predictions with numerical experiments for a disordered boson Hubbard model.     

A New method for studying ion beam mixing

A new method of ion beam mixing is presented. Using the metallic superlattice as a target,-2 X-ray diffraction measurements, and the computer program SLFOR for detailed calculations of X-ray diffraction spectra, it was possible to investigate the spread of mixed regions with an accuracy of a few angstroms. This method has been applied to Bi-Sb and Ag-Cu targets mixed by the use of 250–300 keV Ar²⁺ ions. The mixing parameterD*t/ was estimated to be 43×10³ Å⁴ and 23×10² Å⁴ for Bi-Sb and Ag-Cu superlattices, respectively.     

Electric method for studying reorientation dynamics of the nematic liquid crystal director

A method has been proposed for studying the reorientation dynamics of the nematic liquid crystal (NLC) director using the results of measurements of the electric response of an LC cell. The simulation of the time dependences of the current in an LC cell with a homogeneous orientation is carried out upon variation of the applied voltage, the initial tilt angle of the director, dielectric anisotropy, and the elasticity coefficient, as well as the dynamic viscosity, density, and ion mobility in the NLC. A comparison of the experimental and computational curves of the electric response for NLC 5CB shows their good agreement. The method makes it possible to monitor the steady-state current, the density, and the ion mobility in NLCs.     

A novel method for studying the buckling of nanotubes considering geometrical imperfections

Buckling of nanotubes has been studied using many methods such as molecular dynamics (MD), molecular mechanics, and continuum-based shell theories. In MD, motion of the individual atoms is tracked under applied temperature and pressure, ensuring a reliable estimate of the material response. The response thus simulated varies for individual nanotubes and is only as accurate as the force field used to model the atomic interactions. On the other hand, there exists a rich literature on the understanding of continuum mechanics-based shell theories. Based on the observations on the behavior of nanotubes, there have been a number of shell theory-based approaches to study the buckling of nanotubes. Although some of these methods yield a reasonable estimate of the buckling stress, investigation and comparison of buckled mode shapes obtained from continuum analysis and MD are sparse. Previous studies show that the direct application of shell theories to study nanotube buckling often leads to erroneous results. The present study reveals that a major source of this error can be attributed to the departure of the shape of the nanotube from a perfect cylindrical shell. Analogous to the shell buckling in the macro-scale, in this work, the nanotube is modeled as a thin-shell with initial imperfection. Then, a nonlinear buckling analysis is carried out using the Riks method. It is observed that this proposed approach yields significantly improved estimate of the buckling stress and mode shapes. It is also shown that the present method can account for the variation of buckling stress as a function of the temperature considered. Hence, this can prove to be a robust method for a continuum analysis of nanosystems taking in the effect of variation of temperature as well.     

A new lateral distribution function for electrons in extensive air showers (EAS) detected near sea level

Summary A detailed analysis of Extensive Air Showers in the size range 10⁴–10⁶ particles detected near sea level has yielded a new distribution function for the radial distribution of EAS electrons. The goodness-of-fit criteria applied to the present and already existing similar distribution functions confirm that the present function is appropriate in EAS at radial distances beyond 20 m from the shower axis.