Study of the hadronic component of extensive air showers at the Carpet-2 EAS array

A method for the detection of hadrons with a muon detector at the Carpet-2 EAS array (Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences) has been described. Events induced by cosmic-ray hadrons have a signature that makes it possible to reliably distinguish them from muons. The characteristics of the hadronic component of extensive air showers with N _e ≥ 10⁵ have been presented.     

Classification of ultrahigh-energy extensive air showers in terms of the muon content

Ultrahigh-energy extensive air showers detected at the Yakutsk array are analyzed. Showers different in the muon content are revealed. Four classes of showers are separated.     

Delayed muons in extensive air showers and double-front showers

The results of a long-term experiment performed in the period between 1995 and 2006 with the aid of the MUON-T underground (20 mwe) scintillation facility arranged at the Tien Shan mountain research station at an altitude of 3340 m above sea level are presented. The time distribution of delayed muons with an energy in excess of 5 GeV in extensive air showers of energy not lower than 106 GeV with respect to the shower front was obtained with a high statistical significance in the delay interval between 30 and 150 ns. An effect of the geomagnetic field in detecting delayed muons in extensive air showers was discovered. This effect leads to the asymmetry of their appearance with respect to the north-south direction. The connection between delayed muons and extensive air showers featuring two fronts separated by a time interval of several tens of to two hundred nanoseconds is discussed. This connection gives sufficient grounds to assume that delayed muons originate from the decays of pions and kaons produced in the second, delayed, front of extensive air showers.     

Observation of double extensive air showers

Double extensive air showers were studied at the Tien Shan high-mountain scientific station of the Lebedev Physical Institute using two different installations. One measured the electron-photon shower component, the other measured Cherenkov radiation. Double showers separated by a time interval of ～100 ns were detected by both setups. The frequency of the occurrence of such showers in each setup is analyzed. It is shown that these frequencies are identical when observing vertical showers (the zenith angle ? < 60°).     

Reestimation of the energy of extensive air showers at the Yakutsk EAS array with the CORSIKA package

The responses of ground and underground muon scintillation detectors of the Yakutsk extensive air shower (EAS) array from primary particles with the energy E ₀ ≥ 10¹⁷ eV have been calculated within the QGSJET-01-d, QGSJET-II-04, SIBILL, and EPOS-LHC models with the CORSIKA package. A new estimate obtained for E ₀ is lower by a factor of about 1.41 than that previously obtained within the calorimetric method for EASs.     

Neutron multiplicity: Local hadronic showers and extensive air showers

A detailed analysis of events with neutron multiplicity M = 3−30 on neutron monitors (NMs) in Barentsburg (Spitsbergen), Baksan (North Caucasus), and Apatity (Murmansk region) is performed on the data obtained using a unique new data collection system. It is now possible for the first time to register local showers in cosmic rays on NMs and to investigate their structure with a high precision. Multiplicity on NMs is simulated using the GEANT4 Monte Carlo toolkit. Local hadronic cascades in the atmosphere with transverse sizes of 1 to 6 m were observed for the first time using the NM data. NM multiplicity generated by EAS hadronic cascades is studied on the data set on coupling NMs with the CARPET EAS facility.     

On the angular distribution of extensive air showers

Angular distributions of extensive air showers with different number of charged particles in the range 2.5 × 10⁵–4 × 10⁷ are derived using the experimental data obtained with the EAS MSU array. Possible approximations of the obtained distributions with different empiric functions available in literature, are analyzed. It is shown that the exponential function provides the best approximation of the angular distributions in the sense of the χ² criterion.     

Signals in the underground scintillation detectors of the Yakutsk array from muons of extensive air showers

A model of the underground part of the Yakutsk array was developed. The signals from muon scintillation detectors were calculated using the GEANT4 code within this model. It was shown that the signals strongly fluctuate and may be several times higher that the mean ionization energy losses by a single muon. These large losses imitate high muon multiplicity in the case of a low muon density. It was also shown that there are many gamma particles near the shower axis, which significantly contribute to signals in underground detectors and thus make data interpretation difficult.     

Methods for estimating the energy of extensive air showers

A multilevel scheme for calculating estimates of the energy of extensive air showers on the basis of signals in different detectors is considered. The numerical energy estimates at specified values of signals in scintillation detectors are smaller than the experimental ones by a factor of about 1.6. The results of the calculation confirmed that the total flux of Cherenkov light is proportional to the shower energy. The flux of fluorescent light generated within 100 m from the shower core is due to only 60% of the total energy.     

Kaluza-Klein gravitons at the LHC and in extensive air showers

The small curvature option of the Randall-Sundrum model with two branes is considered which has almost continuous spectrum of low-mass Kaluza-Klein gravitons. It is shown that gravity effects related with these excitations can be detected in double diffractive events at the LHC and in inclined air showers induced by interactions of cosmic neutrinos with atmospheric nucleons at ultra-high energies.     

Investigating hadronic cores of exstensive air showers at the CARPET-2 array

Characteristics of the hadronic component of exstensive air shower (EAS) trunks are investigated at the CARPET-2 array of the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences. In this work, we study showers with axes that located within its muon detector (MD). We discuss the procedure for selecting such showers in our experiment. The relationship between the number of thermal neutrons detected by heat detectors installed in the muon detector’s tunnel and the total energy of a cascade generated by hadrons in the magnetic detector’s absorbent matter is presented.     

Increase in the absorption length of inclined extensive air showers

The dependence of the number of extensive air showers with an energy above 10¹⁸ eV on the zenith angle θ is obtained in groups with a constant solid-angle step. The number of showers first decreases with an increase in the zenith angle and then, after reaching ～5°, increases strongly. With increasing energy, the kink on the dependence of the number of showers on θ is displaced towards larger angles, i.e., in the direction corresponding to the shift of the depth of the cascade-curve maximum.     

Macroscopic model of radio emission from extensive air showers

A macroscopic model of radio emission from extensive air showers is developed. This model is appropriate for calculating this radio emission at frequencies below 100 MHz. It is constructed on the basis of an analysis of the radiation integral and is verified by comparing field observables predicted by the model with the respective results obtained within the microscopic approach to calculating radio emission from extensive air showers.     

Radio emission of extensive air showers at microwave frequencies

It is found that the power of the incoherent radiation of ionization electrons of an extensive air shower in the frequency range of 150 GHz is more than 10^–24 W/m²Hz, with the shower energy ~10¹⁸ eV at a distance of 5 km from its axis. This means that, unlike fluorescent detectors, a radio telescope with an effective area of more than 300 m² can monitor the trajectory of showers with an energy higher than 10¹⁸ eV at any time of the day regardless of the weather. The spectrum maximum near the frequency of 150 GHz is roughly three orders of magnitude higher than the value experimentally measured in the characteristic band (~5-10 GHz).     

Detection and analysis of radio pulses from extensive air showers

Radio pulses from extensive air showers (EAS) at 30, 44, and 60 MHz frequencies have been studied, using wide band broad-side arrays of half-wave dipole antenna systems. The experimental results support the theoretical prediction that the field strength of radio emission depends on the shower size. An asymmetry has been noticed in the pulse height distributions of radio pulses detected by North-South and East-West directed arrays. These observations are in agreement with the theory that the charge separation mechanism is predominant in generating radio pulses from EAS and radio emission is polarised in the East-West direction. Experimental data are compared with those of earlier workers.     

EAS-TOP: Lateral and temporal characteristics of extensive air showers

Summary First results on the lateral and temporal structures of EAS obtained from the EAS-TOP array are presented. A correlation between the slope of the lateral distribution function and the time delay of EAS particles with respect to the shower front at fixed core distance is found and discussed. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Simulations of radio emission from ultrahigh-energy extensive air showers

The radio emission from extensive air showers with energies up to 10¹⁷ eV has been calculated. The calculated lateral distribution of the radio emission is in good agreement with the LOPES-10 experimental data.     

Temporal structure of the muon disk at large distances from the axis of extensive air showers with E 0⩾6 ×1016eV

Preliminary results are reported from an investigation of the temporal structure of the muon disk in extensive air showers (EASs) with primary energy E ₀≥6×10¹⁶eV at distances 100–1500 m from the axis. The investigation is performed at the Yakutsk array using the large muon detector, which commenced operation in November 1995, with a planned area 184 m² and a detection threshold E _μ≈0.5· sec θ GeV. For E ₀>10¹⁸eV it is found that the thickness of the muon disk tends to decrease. This requires substantial changes in our notions of the development of EASs. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 361–366 (25 March 1998)