High-energy cosmic neutrino puzzle: a review.

We appraise the status of high-energy neutrino astronomy and summarize the observations that define the 'IceCube puzzle.' The observations are closing in on the source candidates that may contribute to the observation. We highlight the potential of multi-messenger analysis to assist in the identification of the sources. We also give a brief overview of future search strategies that include the realistic possibility of constructing a next-generation detector larger by one order of magnitude in volume.

Experimental confirmation that the proton is asymptotically a black disk.

Although experimentally accessible energies cannot probe "asymptopia", recent measurements of inelastic pp cross sections at the LHC at 7000 GeV and by Auger at 57,000 GeV allow us to conclude that (i) both σ(inel) and σ(tot), the inelastic and total cross sections for pp and pp interactions, saturate the Froissart bound of ln(2)s, (ii) when s→∞, the ratio σ(inel)/σ(tot) is experimentally determined to be 0.509 ± 0.021, consistent with the value 0.5 required by a black disk at infinite energies, and (iii) when s→∞, the forward scattering amplitude becomes purely imaginary, another requirement for the proton to become a totally absorbing black disk. Experimental verification of the hypotheses of analyticity and unitarity over the center of mass energy range 6 ≤ √s ≤ 57000 GeV are discussed. In QCD, the black disk is naturally made of gluons; our results suggest that the lowest-lying glueball mass is 2.97 ± 0.03 GeV.

Invited review article: IceCube: an instrument for neutrino astronomy.

Neutrino astronomy beyond the Sun was first imagined in the late 1950s; by the 1970s, it was realized that kilometer-scale neutrino detectors were required. The first such instrument, IceCube, is near completion and taking data. The IceCube project transforms 1 km(3) of deep and ultratransparent Antarctic ice into a particle detector. A total of 5160 optical sensors is embedded into a gigaton of Antarctic ice to detect the Cherenkov light emitted by secondary particles produced when neutrinos interact with nuclei in the ice. Each optical sensor is a complete data acquisition system including a phototube, digitization electronics, control and trigger systems, and light-emitting diodes for calibration. The light patterns reveal the type (flavor) of neutrino interaction and the energy and direction of the neutrino, making neutrino astronomy possible. The scientific missions of IceCube include such varied tasks as the search for sources of cosmic rays, the observation of galactic supernova explosions, the search for dark matter, and the study of the neutrinos themselves. These reach energies well beyond those produced with accelerator beams. The outline of this review is as follows: neutrino astronomy and kilometer-scale detectors, high-energy neutrino telescopes: methodologies of neutrino detection, IceCube hardware, high-energy neutrino telescopes: beyond astronomy, and future projects.

Radiography of Earth's core and mantle with atmospheric neutrinos.

A measurement of the absorption of neutrinos with energies in excess of 10 TeV when traversing the Earth is capable of revealing its density distribution. Unfortunately, the existence of beams with sufficient luminosity for the task has been ruled out by the AMANDA South Pole neutrino telescope. In this Letter we point out that, with the advent of second-generation kilometer-scale neutrino detectors, the idea of studying the internal structure of Earth may be revived using atmospheric neutrinos instead.

Neutrino astrophysics experiments beneath the sea and ice.

Neutrino astronomy beyond the Sun was first imagined in the late 1950s. A neutrino detector at the bottom of Lake Baikal, the deployment of detectors in the Mediterranean Sea, and the construction of a kilometer-scale neutrino telescope at the South Pole exemplify current efforts to realize this dream.

AMANDA observations constrain the ultrahigh energy neutrino flux.

A number of experimental techniques are currently being deployed in an effort to make the first detection of ultrahigh energy cosmic neutrinos. To accomplish this goal, techniques using radio and acoustic detectors are being developed, which are optimally designed for studying neutrinos with energies in the PeV-EeV range and above. Data from the AMANDA experiment, in contrast, have been used to place limits on the cosmic neutrino flux at less extreme energies (up to approximately 10 PeV). In this Letter, we show that by adopting a different analysis strategy, optimized for much higher energy neutrinos, the same AMANDA data can be used to place a limit competitive with radio techniques at EeV energies. We also discuss the sensitivity of the IceCube experiment, in various stages of deployment, to ultrahigh energy neutrinos.