Experimental Investigation of Cosmic Ray Nature and Interactions at High-Mountain Stations PAMIR, TIEN SHAN and ARAGATS

The area of articles presented is cosmic ray physics at super-high energies. It includes two subjects: particle interactions at energies unattainable at colliders and nature of the "knee" in the energy spectrum of the primary cosmic radiation around 3x10¹⁵ eV. 

Cosmic rays remain a probe for the inelastic proton-air cross section.  Its value in the region from 0.2 TeV (accelerator experiments with fixed targets) to 10 PeV (cosmic rays) is discussed in paper by N. Nesterova. The comprehensive analysis includes both experimental data on various components of extensive air showers at 0.5-10 PeV from Tien Shan station and model calculations. It is shown that the cross section increase conforms to (7-9) % per one order of energy. That corresponds with the value of the inelastic proton-air cross section:

?_p-air (1 PeV) =  (350±15) mb.

The nature of the "knee" still is a hot problem. In the issue a novel method for "knee" investigation is presented (papers by V. Pavlyuchenko et al.). The method is applied to data obtained in the GAMMA experiment at Aragats station. The analysis provides evidence for the possible existence of a nearby source of primary cosmic rays in the Southern hemisphere. 

Origin of the "knee" is also in the focus of the experiment at Tien Shan station. Hybrid array with X-ray emulsion chamber is used to investigate external air shower cores around the "knee" region (the paper by S. Shaulov et al.). Effects observed may be explained assuming a penetrating component that possibly originates due to the increasing fraction of elastic interactions, that is discovered at the LHC.  

Experiments with X-ray emulsion chambers are used to obtain information about charm particle production in cosmic ray interactions.  Cross section of charm particle production is obtained at Tien Shan and Pamir stations, in high altitude experiments with X-ray emulsion chambers (the paper by A. Borisov et al.). Conclusion is made about rapid increase and high value of charm production cross section: ?= 6,8 mb/nucleon at hadron energies E~ 75 TeV (in the laboratory frame of reference). In the paper, strangelets are also discussed as they can partially contribute to the effects observed in these experiments. 

Important Dates

1. Deadline for Submission: October 9, 2017
2. First Round of Review: October 30, 2017
3. Publication Date: January 01, 2018