On the Dominant Role of Charm Production in the Forward Kinematic Region According to Cosmic-Ray Experiments

A phenomenon of abnormally weak absorption of very-high-energy cosmic-ray hadrons in lead is discussed. This phenomenon was first observed in Tien-Shan high-altitude experiments in hadronic cores of extensive air showers and has encouraged to introduce the hypothesis of a so-called long-flying or penetrating cosmic-ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs. Experiments, which are sensitive to the production of charmed hadrons in the forward kinematic region (xLab ≳ 0.1), have been carried out at the Tien-Shan and Pamirs with exposing two-storey XRECs with large air gaps to prove explanation of the experimental results with high charm production cross section $${\sigma _{pp \to c\bar c}} \sim 8$$ at xLab ≳ 0.1 at ⟨ELab⟩ ∼ 75 TeV. This $${\sigma _{pp \to c\bar c}}$$ value makes it possible to reproduce the experimental hadron-absorption curve observed with XRECs, including curve’s bending at a depth of ∼70 c.u.