Study of charm production in the forward cone at energy ELab ∼ 75 TeV with a two-storey X-ray emulsion chamber exposed at, mountain altitudes

The origin of the cosmic ray hadron excess observed in a deep uniform lead X-ray emulsion chamber (XREC) at depths larger than 70 radiation lengths is analyzed. We present preliminary experimental data on the absorption of cosmic ray hadrons in the two-storey XREC with a large air gap exposed at the Tien Shan mountains. The design of the chamber was especially invented to prove the hypothesis on a substantial increase of the charm particle production cross section with energy at E-Lab similar to 75 TeV as the main source of the darkness spot excess observed on X-ray films. Experimental data obtained with both a 2-storey XREC and a deep uniform XREC are compared with simulation results calculated with the FANSY 1.0 model. The comparison reveals a qualitative agreement between experimental and simulated data under the assumption of high values of charm particle production cross section at E-Lab similar to 75 TeV in the forward kinematic region at x(Lab) > 0.1.