Neutrino-nucleon Total Cross Section Research Articles

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 2 t 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.

Charged current neutrino-nucleon total cross section at high energies

We evaluate the charged current neutrino-nucleon total cross section up to neutrino energies of ${10}^{12}\text{ }\text{ }\mathrm{GeV}$ in the leading order and next-to-leading order of perturbative QCD within the framework of two different factorization schemes. The numerical implications of some inconsistent QCD calculations are illustrated.

Analytical evolution of nucleon structure functions with power corrections at twist-4 and predictions for ultrahigh energy neutrino-nucleon cross section

In this paper we present an analytic result for the evolution in $Q^2$ of the structure functions for the neutrino-nucleon interaction, valid at twist-2 in the region of small values of the Bjorken $x$ variable and for soft non-perturbative input. In the special case of flat initial conditions, we include in the calculation also the contribution of the twist-4 gluon recombination corrections, whose effect in the evolution is explicitly determined. Finally, we estimate the resulting charged-current neutrino-nucleon total cross section and discuss its behavior at ultra-high energies.

Erratum: Enhancement and suppression of the neutrino-nucleon total cross section at ultrahigh energies [Phys. Rev. D68, 054005 (2003)

We argue that high gluon density effects at small $x$ are important for the calculation of ultra-high energy neutrino nucleon cross sections due to the phenomenon of geometric scaling. We calculate the cross section for $\nu N \to \mu X$, including high gluon density effects, using the all twist formalism of McLerran and Venugopalan and show that it can be related to the dipole nucleon cross section measured in DIS experiments. For neutrino energies of $E_{\nu}\sim 10^{12}$ GeV, the geometric scaling region extends all the way up to $Q^2 \sim M^2_{W}$. We show that geometric scaling can lead to an {\it enhancement} of the neutrino nucleon total cross section by 1-2 orders of magnitude compared to the leading twist cross section and discuss the implications for neutrino observatories. At extremely high energies, gluon saturation effects suppress the neutrino nucleon total cross section and lead to its unitarization.

Ultrahigh energy neutrino-nucleon interactions

Ultra-high energy ($E_\nu>10^8 $ GeV) neutrino-nucleon total cross sections $\sigma^{\nu N}$ are estimated from a soft non-perturbative model complemented by an approximate QCD evolution, explicitly calculated. The resulting asymptotic energy behavior of the neutrino-nucleon charged-current total cross section is derived analytically and predictions concerning the observation of ultra-high energy neutrinos in future experiments are presented.

Enhancement and suppression of the neutrino-nucleon total cross section at ultrahigh energies

We argue that high gluon density effects at small x are important for the calculation of ultrahigh energy neutrino-nucleon cross sections due to the phenomenon of geometric scaling. We calculate the cross section for $\ensuremath{\nu}\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\mu}X,$ including high gluon density effects, using the all twist formalism of McLerran and Venugopalan and show that it can be related to the dipole nucleon cross section measured in deep inelastic scattering experiments. For neutrino energies of ${E}_{\ensuremath{\nu}}\ensuremath{\sim}{10}^{12}\mathrm{GeV},$ the geometric scaling region extends all the way up to ${Q}^{2}\ensuremath{\sim}{M}_{W}^{2}.$ We show that geometric scaling can lead to an enhancement of the neutrino-nucleon total cross section by an order of magnitude compared to the leading twist cross section and discuss the implications for neutrino observatories. At extremely high energies, gluon saturation effects suppress the neutrino-nucleon total cross section and lead to its unitarization.

Dynamical QCD predictions for ultrahigh energy neutrino cross sections

Neutrino-nucleon total cross sections for neutrino energies up to ultrahigh energies (UHE), E ν = 10 12, GeV, are evaluated within the framework of the dynamical (radiative) parton model. The expected uncertainties of these predictions do not exceed the level of about 20% at the highest energies where contributions of parton distributions in the yet unmeasured region around x ⋍ 10 −8, to 10 −9 are non-negligible. This is far more accurate than estimated uncertainties of about 2 ±1 due to fixed power law extrapolations of parton distributions to x < 10 −5 required for calculating UHE cosmic neutrino event rates.

Models for weak currents with Han-Nambu three-triplets

A mechanism introduced by Stech to suppress $\ensuremath{\Delta}S=1$ neutral currents is adapted to the Han-Nambu model. Consequences of different schemes arising from the freedom in baryon number assignment are investigated. Though first order processes are eliminated in all of these models, only two of them give sufficiently small second-order rates for ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. In these cases, it is possible to obtain $sin{\ensuremath{\theta}}_{C}=\frac{1}{3\sqrt{2}}\ensuremath{\cong}0.235$ in a rather natural manner. These two models and one of the others can be extended to SU(2)\ensuremath{\bigotimes}U(1) gauge theories of weak and electromagnetic interactions which are anomaly-free in the quark sector and thus require heavy leptons to cancel leptonic anomalies. The rates for neutral events in inclusive neutrino-nucleon reactions predicted by these gauge theories are compatible with experimental results when ${sin}^{2}{\ensuremath{\theta}}_{W}\ensuremath{\cong}\frac{1}{3}$. The models giving acceptable ${K}_{L}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ rates do not predict any enhancement of neutrino-nucleon total cross sections associated with the production of SU(3)\ensuremath{''} nonsinglet states. None of the above schemes helps explain the $\ensuremath{\Delta}T=\frac{1}{2}$ rule.

An estimate of higher order contributions to elastic neutrino-nucleon scattering at CERN-Gargamelle energy

Using information on neutrino nucleon total cross section together with the optical theorem we give an estimate of higher order contributions for elastic nuutrino nucleon scattering at the Gargamelle energy. At the incident neutrino energy of 10 GeV the higher order contributions are for neutrino proton scattering a factor 10 −7 smaller than the first order contribution (10 −9 for neutrin scattering).