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Detectors
Published in C. R. Kitchin, Astrophysical Techniques, 2020
The first astronomical neutrino detector started operating in 1968 (Section 1.5.2.3), and it quickly determined that the observed flux of solar neutrinos was too low by a factor of 3.3 compared with the theoretical predictions. This deficit was confirmed later by other types of detectors such as Soviet-American Gallium Experiment (SAGE), Gallium Experiment (GALLEX) and Kamiokande and became known as the solar neutrino problem. However, these detectors were only sensitive to electron neutrinos. Then, in 1998, the Super-Kamiokande detector found a deficit in the number of muon neutrinos produced by cosmic rays within the Earth’s atmosphere. Some of the muon neutrinos were converting to tau neutrinos during their flight time to the detector. The Super Kamiokande, Sudbury Neutrino Observatory (SNO) and Oscillation Project with Emulsion Tracking Apparatus (OPERA) detectors have since confirmed that all three neutrinos can exchange their identities (Figure 1.105)135. The solar neutrino problem has thus disappeared because two-thirds of the electron neutrinos produced by the Sun have changed to muon and tau neutrinos by the time that they reach the Earth and so were not detected during the early experiments. The current IceCube neutrino detector and more probably its 2022–2023 upgrade (Section 1.5.2) are soon likely to detect high-energy astrophysical tau neutrinos arising from oscillations of the high-energy electron neutrinos already detected.
New Energy Sources
Published in Fang Lin Luo, Hong Ye, Renewable Energy Systems, 2013
Solar neutrinos originate from the nuclear fusion powering the Sun and other stars. The details of the operation of the Sun are explained by the Standard Solar Model. In short, when four protons fuse to become one helium nucleus, two of them have to convert into neutrons, and each such conversion releases one electron neutrino.
The Authority of Science: Knowledge, Truth and Reality
Published in Steven Yearley, Science, Technology, and Social Change, 2014
In some ways, however, it might be argued that these objections to the idea of the primacy of observation are contrived; they are not real difficulties but are made–up problems. Academics, it might be said, often appear to be attracted to made-up problems like the stereotypical philosopher’s anxiety that all life might be a dream. But these problems are not fictional ones; they do have a relevance for at least two reasons. First, the kind of certainty which the factual foundation of science is supposed to offer is an ‘in principle’ kind. The factual basis of science should secure it even against imagined challenges or ‘thought experiments’. Turning back for the moment to the implied contrast with moral relativism, we can easily imagine that claims to the effect that sexual practices or gender roles might be different would seem far–fetched in a morally closed society. Suggestions that women might participate in government might be seen as all too dreamlike. Yet we would not respect the argument that these challenges to morality were ‘contrived’ or ‘fanciful’. Absolute moral certainty crumbles once one accepts the principle that all our beliefs could reasonably be otherwise. So too does the naive confidence in the factual basis of scientific belief. Second, and more persuasively, it is anyway the case that just these sorts of issues do get questioned in scientific disputes. The study of controversies has been one of the principal areas of investigation in recent years by sociologists of science precisely because the apparent certainty of observation is undermined in these circumstances (Collins, 1981; Mulkay, 1980). In a recent study of solar neutrinos Pinch (1981) has provided a valuable example of these kind of factors. Solar neutrinos are curious, virtually massless and chargeless particles, generated as a by–product of the nuclear reactions in the sun, which travel through space to the earth. They are of interest because of the information they can impart about the nature of the sun. Pinch reports however that a conflict exists between the expected flux of these particles, based on other sources of knowledge about the form of reaction proceeding in the sun, and the actual measures of the flux. In such a clash of interpretations the observation of the flux at the earth’s surface might be expected to take precedence; it is after all an observation.
Light, the universe and everything – 12 Herculean tasks for quantum cowboys and black diamond skiers
Published in Journal of Modern Optics, 2018
Girish Agarwal, Roland E. Allen, Iva Bezděková, Robert W. Boyd, Goong Chen, Ronald Hanson, Dean L. Hawthorne, Philip Hemmer, Moochan B. Kim, Olga Kocharovskaya, David M. Lee, Sebastian K. Lidström, Suzy Lidström, Harald Losert, Helmut Maier, John W. Neuberger, Miles J. Padgett, Mark Raizen, Surjeet Rajendran, Ernst Rasel, Wolfgang P. Schleich, Marlan O. Scully, Gavriil Shchedrin, Gennady Shvets, Alexei V. Sokolov, Anatoly Svidzinsky, Ronald L. Walsworth, Rainer Weiss, Frank Wilczek, Alan E. Willner, Eli Yablonovitch, Nikolay Zheludev
This background can be overcome if the direction of the nuclear recoil from a scattering event is identified. The direction of the solar neutrino flux is known while the dark matter flux should be isotropic. By vetoing events that correspond to incident particles emerging from the known location of the Sun, the isotropic dark matter flux can be identified. It is important to be able to measure the recoil direction at solid-state densities since large target masses are necessary to detect the small WIMP cross sections. Crystal defects such as nitrogen-vacancy centres in diamond, paramagnetic F-centres in metal halides and defects in silicon carbide could potentially be used to identify the direction of WIMP-induced nuclear recoil [206]. The detection idea is the following – when the WIMP scatters, the induced nuclear recoil creates a tell-tale damage cluster, localized to within 50 nm, that correlates well with the direction of the recoil. This damage cluster induces strain in the crystal, changing the energy levels of crystal defects such as nitrogen-vacancy centres. This level change can be measured optically (or through paramagnetic resonance) making it possible detect the strain environment around the defect in a solid sample. It is experimentally possible to create a high density of these defects, and nanoscale resolution of defect properties has also been demonstrated [271] [68,122,143,210,305]. To identify the direction of a nuclear recoil, we can first use conventional WIMP detection ideas such as the collection of ionization/scintillation to identify potential dark matter events. Once an event is identified, the defects in the vicinity of the event will be interrogated (for example, optically) to determine the strain environment, thus identifying the direction of the recoil (see Figure 26). If successful, this concept would open a new path to continue to probe the theoretically well-motivated WIMP. It would also be a novel application of a quantum sensor such as the spin of a nitrogen-vacancy centre for a particle physics application.