Effects of charged Higgs bosons in the deep inelastic process \nu_{\tau}   {\cal N} \to \tau^- X and the possibility of detecting tau-neutrinos at   cosmic neutrino detectors
  We study the deep inelastic process $\nu_{\tau} + {\cal N} \to \tau^{-} + X$ (with ${\cal N} \equiv (n+p)/2$ 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 the strong dependence of such contribution on $\tan\beta$ and $M_{H^{\pm}}$. We show that in the region $50 \leq \tan\beta \leq 200$ and 90 GeV $\leq M_{H^{\pm}}\leq$ 600 GeV with the additional experimental constraint on the involved model parameters $M_{H^{\pm}} \geq 1.5 \times \tan\beta$ GeV, the contribution of the charged Higgs boson exchange diagrams to the cross section of the charged current inclusive $\nu_{\tau} {\cal N}$ collision can become important. We obtain that this contribution for an inclusive dispersion generated through the collision of an ultrahigh energy tau-neutrino with $E_{\nu} \approx 10^{20}$ eV on a target nucleon can be larger than the value of the contribution of the $W^{\pm}$ exchange diagrams, provided that $M_{H^{\pm}} \approx 300$ GeV and $\tan\beta \approx 200$. 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. 
A. Rosado