Investigation of EAS cores

Abstract

The development of nuclear-electromagnetic cascade models in air in the late forties have shown informational content of the study of cores of extensive air showers (EAS). These investigations were the main goal in different experiments which were carried out over many years by a variety of methods. Outcomes of such investigations obtained in the HADRON experiment using an X-ray emulsion chamber (XREC) as a core detector are considered. The N e spectrum of EAS associated with γ-ray families, spectra of γ-rays (hadrons) in EAS cores and the N e dependence of the muon number, N µ , in EAS with γ-ray families are obtained for the first time at energies of 10 15-10 17 eV with this method. A number of new effects were observed, namely, an abnormal scaling violation in hadron spectra which are fundamentally different from model predictions, an excess of muon number in EAS associated with γ-ray families, and the penetrating component in EAS cores. It is supposed that the abnormal behavior of γ-ray spectra and N e dependence of the muon number are explained by the emergence of a penetrating component in the 1st PCR spectrum 'knee' range. Nuclear and astrophysical explanations of the origin of the penetrating component are discussed. The necessity of considering the contribution of a single close cosmic-ray source to explain the PCR spectrum in the knee range is noted.

Scaling violation in interaction of cosmic ray hadrons and the nature of the 3 PeV knee in the spectrum of primary cosmic rays

“…As for the relatively long-living charged pions (τ 10 −8 s in the rest frame) and baryons of EAS core, they can reach the installation level and interact within the internal material of XREC, which results, again, in development of an electromagnetic cascade in the lead absorber. Since the total thickness of the Tien Shan XREC was not well enough for effective absorption of high energy hadrons, in a part of the whole exposition an additional 60 cm thick target of carbon enriched rubber ((CH) n ) was placed between the two similar XREC units stacked one above the other [19,20]. Thus, the electromagnetic cascades in the upper unit (Γblock) were mostly generated by the gamma rays from high energy π 0 decays in the atmosphere, while the neutral pions from hadronic interactions in the rubber target were detected in analogous manner in the lower unit (Hblock).…”

“…2), and along the circles with 20 m, 50 m, and 80 m radii circumscribed around this center. All detectors were made of the (0.5 × 0.5×0.05) m 3 blocks of solid polystyrene scintillator [20,35,36]. In the case of an EAS event the sum amplitude of scintillation flash generated in such detector is proportional to the amount of charged particles which have passed through the point of detector location, so registration of those amplitudes in a system of synchronously operating detectors gives the spatial distribution of particles density in a shower.…”

“…The Tien Shan calorimeter was later replaced by a 160 m 2 large X-ray emulsion chamber (XREC). This modification was made in the frames of the experiment HAD- RON (1985RON ( -1991 which united the X-ray films and EAS detection methods in a single hybrid installation [19,20]. Together with essential increase of the size of continuous area of EAS cores detection, the XREC permitted to measure directly the individual energy of the TeV scale gamma ray quanta inside EAS core, and to study their characteristics in dependence on the total number of EAS electrons N e (generally named as EAS size), as well as on the energy E 0 of the primary cosmic ray particle which had created the EAS.…”

Nucleus-nucleus interactions in very-high-energy cosmic ray experiments

“…Possible reasons of their appearance were discussed in many papers, and various ideas of their explanation were proposed, see e.g. [8][9][10][11][12]. But no idea for their explanation from a single point of view was proposed.…”

The rise of muon content in extensive air showers after the 3 PeV knee of the primary cosmic ray spectrum according to data of the Tien Shan mountain installation

“…Investigation of the muon component of EAS has remained one of the main directions of experimental activity at the Tien Shan mountain cosmic ray station of LPI over the whole history of its existence. During the four last decades such studies were made here in the frames of two absolutely different experiments: in the years 1985-1991, at the muon hodoscope which was a part of the complex installation HADRON [8,9,10], and later on, since the beginning of 2000s and up to the present time, when registration of the signals of muon passage was continued there at an underground neutron detector [11,12,13,14]. Since the year 2015 the underground detector operates together with a system of shower particles detectors [15] specially for the investigation purpose of the muon component of EAS.…”