Study of the primary cosmic ray mass composition using gamma rays

Abstract

Context. The gamma rays detected by passive balloon-borne emulsion chambers in the stratosphere give additional information on primary cosmic ray composition and allow indirect testing of the conclusions based on the study of the primary particle tracks. Aims. We search for a consistent view of the balloon experiments with traditional calorimeter-type emulsion conducted at various atmospheric depths in the stratosphere. Using analytical calculation, we test two models of primary composition based on experimental information given by these experiments. Methods. We analyze original experimental data relevant for the inquiry, consider the risk of empirical and methodical bias, and test the consistency of data sets with different hypotheses. Results. It is shown that observed experimental data on gamma rays are in agreement with the atmospheric origin of their production. We notice that observed experimental signals in the energy region above 10 TeV can be an indication of an increase of heavy primaries. However, quantitative analysis does not show statistically significant evidence in favor of one specific composition model.

Cosmic ray primary composition in the energy range 10–1000 TeV obtained by passive balloon-borne detector: Reanalysis of the RUNJOB experiment

“…We can notice three distinctive groups in the energy region 8-3000 TeV for protons: (1) in the first two bins (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) TeV) the number of counts in experiment is much lower than that in simulation; (2) in bins 3-6 (26-500 TeV) the number of counts in experiment is very close to the expected mean values (averaged over the 160 000 runs, see Appendix B) in simulation; (3) experiment and TABLE IV. Fluxes and raw number of protons from RUNJOB 1995-1996 flights reported by [5].…”

“…Considering an individual shower, it is impossible to determine whether it is originated by a primary proton or by a nucleon from a heavy primary nucleus. It could indicate the arrival of a cosmic ray family produced by a heavy primary nucleus [22,44]. In general (not only for 1 PeVevent), if secondary nucleons from heavy primaries were accounted as protons, some heavy primaries would be missing.…”

“…Subsequently, it was realized that, in order to construct a consistent view on the RUNJOB experiment itself, to search for patterns, we must look at the complete data sets (particle tracks and gamma rays), as they were presented and published. It was demonstrated that the RUNJOB data on gamma rays were at variance with the RUNJOB conclusions based on primary particle tracks [21,22]. It was shown that the observed gamma rays above 10 TeV can be an indication of an increase of heavy primaries [22].…”

“…It was demonstrated that the RUNJOB data on gamma rays were at variance with the RUNJOB conclusions based on primary particle tracks [21,22]. It was shown that the observed gamma rays above 10 TeV can be an indication of an increase of heavy primaries [22]. While the analysis was under way, there was startling [23] news that RUNJOB already published a so-called ''final'' report [4].…”