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The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the atmospheric muon charge ratio R μ = N μ + /N μ − in the TeV energy region. We analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime during the 2008 CNGS run. We computed separately the muon charge ratio for single and for multiple muon events in order to select different energy regions of the primary cosmic ray spectrum and to test the R μ dependence on the primary composition. The measured R μ values were corrected taking into account the charge-misidentification errors. Data have also been grouped in five bins of the "vertical surface energy" E μ cos θ . A fit to a simplified model of muon production in the atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.

: We present the results of a study performed on the interactions of 10.6A GeV gold nuclei in nuclear emulsions. In a minimum bias sample of 1311 interactions, 5260 helium nuclei and 2622 heavy fragments were observed as Au projectile fragments. The experimental data are analyzed with particular emphasis of target separation interactions in emulsions and study of critical exponents. Multiplicity distributions of the fast-moving projectile fragments are investigated. Charged fragment moments, conditional moments as well as two and three -body asymmetries of the fast moving projectile particles are determined in terms of the total charge remaining bound in the multiply charged projectile fragments. Some differences in the average yields of helium nuclei and heavier fragments are observed, which may be attributed to a target effect. However, two and three-body asymmetries and conditional moments indicate that the breakup mechanism of the projectile seems to be independent of target mass. We looked for evidence of critical point observable in finite nuclei by study the resulting charged fragments distributions. We have obtained the values for the critical exponents γ, β and τ and compare our results with those at lower energy experiment (1.0A GeV data). The values suggest that a phase transition like behavior, is observed .

The results of investigations of the dissociation of a 14 N nucleus of momentum 2.86 A GeV/c in photo-emulsion are presented. The main characteristics of these reactions, that is the cross sections for various fragmentation channels, are given. The fragmentation was analyzed by means of an invariant approach. The momentum and correlation characteristics of α particles for the 14 N→3α+X channel in the laboratory system and the rest systems of 3α particles were considered.The results obtained for the 14 N nucleus are compared with similar data for the 12 C and 16 O nuclei.