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Register a new userHard Pomeron Enhanced Cascade Production and Flux Shadowing in High-Energy Neutrino Astrophysics
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Various implications of new, non-perturbative pomeron inspired enhancement of small-x neutrino-nucleon structure functions for high-energy neutrino astrophysics are discussed. At x larger than 10^{-5} these functions are given by perturbative QCD, while at lower x they are determined by a specific generalization of F_2^{ep}(x,Q^2) description, proposed by A. Donnachie and P. V. Landshoff (their two-component model comprises hard and soft pomerons), to neutrino-nucleon scattering case. We found that i) such enhancement causes the most rapid growth of neutrino-nucleon cross-sections at high energies, ii) pomeron effects may be perceptible in the rates of neutrino induced events in future giant detectors and iii) the rate of high-energy neutrino flux evolution (due to absorption (CC+NC) and regeneration (NC)) on its pass through a large column depth of matter may be subjected to additional influence of hard pomeron. Solving transport equations for the initially power-law decreasing neutrino spectra, we have evaluated shadow factors for several column depths and spectrum indices. The results are compared with analogous calculations, performed within a trivial small-x extrapolation of structure functions. Hard pomeron enhanced high-energy shadow factors are found to be many orders of magnitude lower than those obtained within ordinary perturbative QCD.
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Neutrinos are unique cosmic messengers. Present attempts are directed to extend the window of cosmic neutrino observation from low energies (Sun, supernovae) to much higher energies. The aim is to study the most violent processes in the Universe which accelerate charged particles to highest energies, far beyond the reach of laboratory experiments on Earth. These processes must be accompanied by the emission of neutrinos. Neutrinos are electrically neutral and interact only weakly with ordinary matter; they thus propagate through the Universe without absorption or deflection, pointing back to their origin. Their feeble interaction, however, makes them extremely difficult to detect. The years 2008-2010 have witnessed remarkable steps in developing high energy neutrino telescopes. In 2010, the cubic-kilometre neutrino telescope IceCube at the South Pole has been completed. In the Mediterranean Sea the first-generation neutrino telescope ANTARES takes data since 2008, and efforts are directed towards KM3NeT, a telescope on the scale of several cubic kilometres. The next years will be key years for opening the neutrino window to the high energy Universe. With an instrumented volume of a cubic kilometre, IceCube is entering a region with realistic discovery potential. Discoveries or non-discoveries of IceCube will have a strong impact on the future of the field and possibly mark a moment of truth. In this review, we discuss the scientific case for neutrino telescopes, describe the detection principle and its implementation in first- and second-generation installations and finally collect the existing physics results and the expectations for future detectors. We conclude with an outlook to alternative detection methods, in particular for neutrinos of extremely high energies.
The field of high energy neutrino astrophysics is entering an exciting new phase as two new large-scale observatories prepare to come on line. Both DUMAND (Deep Underwater Muon and Neutrino Detector) and AMANDA (Antarctic Muon and Neutrino Detector) had major deployment efforts in 12/93--1/94. Results were mixed, with both projects making substantial progress, but encountering setbacks that delayed full-scale operation. The achievements, status, and plans (as of 10/94) of these two projects will be discussed.
We discuss the inclusive dilepton cross section for proton (quark)-nucleus collisions at high energies in the very forward rapidity region. Starting from the calculation in the quasi-classical approximation, we include low-x evolution effects in the nucleus and predict leading twist shadowing together with anomalous scaling behaviour.
The energy--zenith angular event distribution in a neutrino telescope provides a unique tool to determine at the same time the neutrino-nucleon cross section at extreme kinematical regions, and the high energy neutrino flux. By using a simple parametrization for fluxes and cross sections, we present a sensitivity analysis for the case of a km^3 neutrino telescope. In particular, we consider the specific case of an under-water Mediterranean telescope placed at the NEMO site, although most of our results also apply to an under-ice detector such as IceCube. We determine the sensitivity to departures from standard values of the cross sections above 1 PeV which can be probed independently from an a-priori knowledge of the normalization and energy dependence of the flux. We also stress that the capability to tag downgoing neutrino showers in the PeV range against the cosmic ray induced background of penetrating muons appears to be a crucial requirement to derive meaningful constraints on the cross section.
Studies on neutrino-nucleon ($ u N$) cross sections at different energy scales have regained interest due to increasing importance of precision measurements, as they are needed as an ingredient in all neutrino experiments. In this paper we have calculated both charged current (CC) and neutral current (NC) $ u$N scattering cross sections at Ultra High Energy (UHE) regime in the neutrino energy ($E_{ u}$) region i.e. $10^{9} GeV le E_{ u} le 10^{12}$ GeV using QCD inspired double asymptotic limit fit of electron-proton structure function $F_{2}^{ep}$ to low $mathit{x}$ HERA data. The form $F_{2}^{ep} sim x^{-lambda(Q^{2})}$ used in our analysis, can be conjectured like a dynamic pomeron (DP)-type behaviour. We also find an analytic form of the total cross sections, $sigma_{CC}^{ u N}$ and $sigma_{NC}^{ u N}$ which appear to be of hard-pomeron exchange types. A comparative analysis of our results with those available in literature is also done. An improved understanding of $ u N$ interactions at UHE are essentially important for future oscillation experiments. Future measurements will support/confront our predictions. textbf{Keywords}: Neutrino cross section, Ultra High Energy, QCD, Double Asymptotic limit, dynamic pomeron, hard-pomeron.
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