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Register a new userDUMAND and AMANDA: High Energy Neutrino Astrophysics
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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.
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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.
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.
We report on searches for neutrino sources at energies above 200 GeV in the Northern sky of the galactic plane, using the data collected by the South Pole neutrino telescopes IceCube and AMANDA. The galactic region considered here includes the Local Arm towards the Cygnus region and our closest approach to the Perseus Arm. The data have been collected between 2007 and 2009 when AMANDA was an integrated part of IceCube, which was still under construction and operated with 22-strings (2007-8) and 40-strings (2008-9) of optical modules deployed in the ice. By combining the larger IceCube detector with the lower energy threshold of the more compact AMANDA detector, we obtain an improved sensitivity at energies below $sim$10 TeV with respect to previous searches. The analyses presented here are: a scan for point sources within the galactic plane; a search optimized for multiple and extended sources in the Cygnus region, which might be below the sensitivity of the point source scan; and studies of seven pre-selected neutrino source candidates. For one of them, Cygnus X-3, a time-dependent search for neutrinos in coincidence with observed radio and X-ray flares has been performed. No evidence of a signal is found, and upper limits are reported for each of the searches. We investigate neutrino spectra proportional to E$^{-2}$ and E$^{-3}$ to cover the entire range of possible spectra. The soft E$^{-3}$ spectrum results in an energy distribution similar to a source with cut-off below $sim$50 TeV. For the considered region of the galactic plane, the 90% confidence level muon neutrino flux upper limits are in the range E$^3$dN/dE$sim 5.4 - 19.5 times 10^{-11} rm{TeV^{2} cm^{-2} s^{-1}}$ for point-like neutrino sources in the energy region [180.0 GeV - 20.5 TeV]. These represent the most stringent upper limits for soft-spectra neutrino sources within the Galaxy reported to date.
Modern astrophysics, especially at GeV energy scales and above is a typical example where several disciplines meet: The location and distribution of the sources is the domain of astronomy. At distances corresponding to significant redshift cosmological aspects such as the expansion history come into play. Finally, the emission mechanisms and subsequent propagation of produced high energy particles is at least partly the domain of particle physics, in particular if new phenomena beyond the Standard Model are probed that require base lines and/or energies unattained in the laboratory. In this contribution we focus on three examples: Highest energy cosmic rays, tests of the Lorentz symmetry and the search for new light photon-like states in the spectra of active galaxies.
In this paper, after a short introduction to the physics of neutrino telescopes, we will report on first performances of the IceCube detector and a selection of preliminary results obtained from data taken while IceCube operated in a partially completed configuration (22 strings and 40 strings). We will emphasize new analysis methods recently developed for the study of the Southern Hemisphere as well as for extended regions. Based on the long term experience of AMANDA and IceCube, the South Pole ice has proven to be an ideal site for astroparticle physics. New ideas and projects about the future beyond IceCube will conclude this presentation.
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