We study the deep inelastic process ντ + N → τ− + X (with N ≡ (n + p)/2 an isoscalar nucleon), in the context of the two-Higgs doublet model Type II (2HDM(II)). We discuss the contribution to the total cross-section of diagrams, in which a charged Higgs boson is exchanged. We present results which show strong dependence of such contributions on tan β and MH±. We show that for tan β ≈ 150 and MH± ≈ 300 GeV, the contribution of the charged Higgs boson exchange diagrams to the cross-section of the charged current inclusive ντN collision can become important. We find that this contribution for an inclusive dispersion generated through the collision of an ultra-high-energy tau-neutrino with Eν ≈ 1021 eV on a target nucleon can be as large as 40% of the value of the contribution of the W± exchange diagrams, provided MH± ≈ 300 GeV and tan β ≈ 150. Such enhancement and the induced variation on the mean inelasticity 〈y〉CC could lead to sizeable effects in the acceptance of cosmic tau-neutrino detectors at experiments such as HiRes, PAO, and the CRTNT, which are anchored to the ground, and at experiments such as EUSO and OWL, which are proposed to orbit around the Earth. We also compare the contribution to σH+tot from the different allowed initial quarks and we show that the contribution from the bottom quark dominates by far. This means that the H± contribution practically always gives a top quark in the final state. Such a large component of the cross-section having a top quark event in the final state could have recognizable features in the EAS experiments.
