Heavy quark currents in ultra-high energy neutrino interactions

We discuss heavy quark contributions to the neutrino-nucleon total cross section at very high energies, well above the real top production threshold. The top-bottom weak current is found to generate strong left-right asymmetry of neutrino-nucleon interactions. We separate contributions of different helicity states and make use of the κ-factorization to derive simple and practically useful formulas for the left-handed (F _L ) and right-handed (F _R ) components of the conventional structure function 2xF ₃ = F _L − F _R in terms of the integrated gluon density. We show that F _L ≫ F _R and, consequently, xF ₃ ≈ F _T , where F _T is the transverse structure function. The conventional structure function F ₂ = F _S + F _T at Q ² ≪ m _t ² appears to be dominated by its scalar (also known as longitudinal) component F _S and the hierarchy F _S ≫ F _L ≫ F _R arises naturally. We evaluate the total neutrino-nucleon cross section at ultra-high energies within the color dipole BFKL-formalism.