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Register a new userCosmic Neutrino Pevatrons: A Brand New Pathway to Astronomy, Astrophysics, and Particle Physics
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The announcement by the IceCube Collaboration of the observation of 28 cosmic neutrino candidates has been greeted with a great deal of justified excitement. The data reported so far depart by 4.3sigma from the expected atmospheric neutrino background, which raises the obvious question: Where in the Cosmos are these neutrinos coming from? We review the many possibilities which have been explored in the literature to address this question, including origins at either Galactic or extragalactic celestial objects. For completeness, we also briefly discuss new physics processes which may either explain or be constrained by IceCube data.
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Neutrino astronomy has entered an exciting time with the completion of the first km3-scale neutrino telescope at the South Pole (IceCube) and the successful operation of the first under-sea neutrino telescope in the Mediterranean (Antares). This new generation of experiments is approaching the sensitivity levels required to explore at least part of the current landscape of neutrino flux predictions from astrophysical sources, bringing neutrino astronomy on the verge of its first discovery. This contribution presents the current status and latest results of the operating neutrino telescopes, with a particular emphasis on the link with the phenomenology of high-energy cosmic rays.
The study of neutrinos is fundamental to connect astrophysics and elementary particle physics. In this last decade solar neutrino experiments and KamLAND confirmed the LMA solution and further clarified the mass and oscillation pattern. Borexino attacked also the study of the low energy neutrino spectrum. However, important points still need clarification, like the apparent anomaly in the vacuum to matter transition region. Besides, a more detailed study of the low energy components of the pp cycle, combined with a measurement of CNO fluxes, is compulsory, also to discriminate between the low and the high
Discovering neutrino decay would be strong evidence of physics beyond the Standard Model. Presently, there are only lax lower limits on the lifetime $tau$ of neutrinos, of $tau/m sim 10^{-3}$ s eV$^{-1}$ or worse, where $m$ is the unknown neutrino mass. High-energy cosmic neutrinos, with TeV-PeV energies, offer superior sensitivity to decay due to their cosmological-scale baselines. To tap into it, we employ a promising method, recently proposed, that uses the Glashow resonance $bar{ u}_e + e to W$, triggered by $bar{ u}_e$ of 6.3 PeV, to test decay with only a handful of detected events. If most of the $ u_1$ and $ u_2$ decay into $ u_3$ en route to Earth, no Glashow resonance would occur in neutrino telescopes, because the remaining $ u_3$ have only a tiny electron-flavor content. We turn this around and use the recent first detection of a Glashow resonance candidate in IceCube to place new lower limits on the lifetimes of $ u_1$ and $ u_2$. For $ u_2$, our limit is the current best. For $ u_1$, our limit is close to the current best and, with the imminent detection of a second Glashow resonance, will vastly surpass it.
This article reviews the progress made over the last 20 years in the development and applications of liquid xenon detectors in particle physics, astrophysics and medical imaging experiments. We begin with a summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information. After a brief introduction of the different type of liquid xenon detectors, we continue with a review of past, current and future experiments using liquid xenon to search for rare processes and to image radiation in space and in medicine. We will introduce each application with a brief survey of the underlying scientific motivation and experimental requirements, before reviewing the basic characteristics and expected performance of each experiment. Within this decade it appears likely that large volume liquid xenon detectors operated in different modes will contribute to answering some of the most fundamental questions in particle physics, astrophysics and cosmology, fulfilling the most demanding detection challenges. From experiments like MEG, currently the largest liquid xenon scintillation detector in operation, dedicated to the rare mu -> e + gamma decay, to the future XMASS which also exploits only liquid xenon scintillation to address an ambitious program of rare event searches, to the class of time projection chambers like XENON and EXO which exploit both scintillation and ionization of liquid xenon for dark matter and neutrinoless double beta decay, respectively, we anticipate unrivaled performance and important contributions to physics in the next few years.
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.
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