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A neutrino is a fermion that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles excluding massless particles. The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.
Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a specific lepton family number can later be measured to have a different lepton family number. The probability of measuring a particular flavor for a neutrino varies between three known states, as it propagates through space.
The Liquid Scintillator Neutrino Detector (LSND) was a scintillation counter at Los Alamos National Laboratory that measured the number of neutrinos being produced by an accelerator neutrino source. The LSND project was created to look for evidence of neutrino oscillation, and its results conflict with the standard model expectation of only three neutrino flavors, when considered in the context of other solar and atmospheric neutrino oscillation experiments. Cosmological data bound the mass of the sterile neutrino to ms < 0.26eV (0.44eV) at 95% (99.9%) confidence limit, excluding at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. The controversial LSND result was tested by the MiniBooNE experiment at Fermilab which has found similar evidence for oscillations. The hint is currently undergoing further tests at MicroBooNE at Fermilab.
The Kamioka Liquid Scintillator Antineutrino Detector (KamLAND) is an electron antineutrino detector at the Kamioka Observatory, an underground neutrino detection facility in Hida, Gifu, Japan. The device is situated in a drift mine shaft in the old KamiokaNDE cavity in the Japanese Alps. The site is surrounded by 53 Japanese commercial nuclear reactors. Nuclear reactors produce electron antineutrinos () during the decay of radioactive fission products in the nuclear fuel. Like the intensity of light from a light bulb or a distant star, the isotropically-emitted flux decreases at 1/R2 per increasing distance R from the reactor. The device is sensitive up to an estimated 25% of antineutrinos from nuclear reactors that exceed the threshold energy of 1.8 megaelectronvolts (MeV) and thus produces a signal in the detector.
Sterile neutrinos are hypothetical particles that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term sterile neutrino is used to distinguish them from the known active neutrinos in the Standard Model, which carry an isospin charge of ±+1/ 2 under the weak interaction. It typically refers to neutrinos with right-handed chirality, which may be added to the Standard Model. Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang Nucleosynthesis are often called neutral heavy leptons (NHLs) or heavy neutral leptons (HNLs).
MiniBooNE is an Cherenkov detector experiment at Fermilab designed to observe neutrino oscillations. A neutrino beam consisting primarily of muon neutrinos is directed at a detector filled with 800 tons of mineral oil and lined with 1,280 photomultiplier tubes. An excess of electron neutrino events in the detector would support the neutrino oscillation interpretation of the LSND result.
Main injector neutrino oscillation search (MINOS) was a particle physics experiment designed to study the phenomena of neutrino oscillations, first discovered by a Super-Kamiokande (Super-K) experiment in 1998. Neutrinos produced by the NuMI beamline at Fermilab near Chicago are observed at two detectors, one very close to where the beam is produced, and another much larger detector 735 km away in northern Minnesota.
The Mikheyev–Smirnov–Wolfenstein effect is a particle physics process which can act to modify neutrino oscillations in matter. The MSF effect is broadly analogous to how soundwaves suffer differential retardation in a variably dense substrate. However it also concerns three separate quantum fields at the same time, whose waves advance at different rates because of a mass difference.
The timeline of particle physics lists the sequence of particle physics theories and discoveries in chronological order. The most modern developments follow the scientific development of the discipline of particle physics.
SciBar Booster Neutrino Experiment (SciBooNE), was a neutrino experiment located at the Fermi National Accelerator Laboratory (Fermilab) in the USA. It observed neutrinos of the Fermilab Booster Neutrino Beam (BNB) that are produced when protons from the Fermilab Booster-accelerator were made to hit a beryllium target; this led to the production of many short-lived particles that decayed into neutrinos. The SciBooNE detector was located some 100 meters downrange from the beryllium target, with a 50 meter decay-volume and absorber combined with 50 meters of solid ground between the target and the detector to absorb other particles than neutrinos. The neutrino-beam continued through SciBooNE and ground to the MiniBooNE-detector, located some 540 meters downrange from the target.
Borexino is a particle physics experiment to study low energy (sub-MeV) solar neutrinos. The detector is the world's most radio-pure liquid scintillator calorimeter. It is placed within a stainless steel sphere which holds the photomultiplier tubes (PMTs) used as signal detectors and is shielded by a water tank to protect it against external radiation and tag incoming cosmic muons that manage to penetrate the overburden of the mountain above.
Lorentz-violating neutrino oscillation refers to the quantum phenomenon of neutrino oscillations described in a framework that allows the breakdown of Lorentz invariance. Today, neutrino oscillation or change of one type of neutrino into another is an experimentally verified fact; however, the details of the underlying theory responsible for these processes remain an open issue and an active field of study. The conventional model of neutrino oscillations assumes that neutrinos are massive, which provides a successful description of a wide variety of experiments; however, there are a few oscillation signals that cannot be accommodated within this model, which motivates the study of other descriptions. In a theory with Lorentz violation, neutrinos can oscillate with and without masses and many other novel effects described below appear. The generalization of the theory by incorporating Lorentz violation has shown to provide alternative scenarios to explain all the established experimental data through the construction of global models.
The K2K experiment was a neutrino experiment that ran from June 1999 to November 2004. It used muon neutrinos from a well-controlled and well-understood beam to verify the oscillations previously observed by Super-Kamiokande using atmospheric neutrinos. This was the first positive measurement of neutrino oscillations in which both the source and detector were fully under experimenters' control. Previous experiments relied on neutrinos from the Sun or from cosmic sources. The experiment found oscillation parameters which were consistent with those measured by Super-Kamiokande.
Antonio Ereditato is an Italian physicist, Visiting Professor at the University of Yale, USA and Emeritus professor at the University of Bern, Switzerland, where he has been Director of the Laboratory for High Energy Physics from 2006 to 2020. He carried out research activities in the field of experimental neutrino physics, of weak interactions and strong interactions with experiments conducted at CERN, in Japan, at Fermilab in United States and at the LNGS in Italy. Ereditato has accomplished several R&D studies on particle detectors: wire chambers, calorimeters, time projection chambers, nuclear emulsions, detectors for medical applications.
Modern searches for Lorentz violation are scientific studies that look for deviations from Lorentz invariance or symmetry, a set of fundamental frameworks that underpin modern science and fundamental physics in particular. These studies try to determine whether violations or exceptions might exist for well-known physical laws such as special relativity and CPT symmetry, as predicted by some variations of quantum gravity, string theory, and some alternatives to general relativity.
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a proposed water Cherenkov detector experiment designed to examine the nature of neutrino interactions. This experiment will study phenomena like proton decay, and neutrino oscillations, by analyzing neutrino interactions in gadolinium-loaded water and measuring their neutron yield. Neutron Tagging plays an important role in background rejection from atmospheric neutrinos. By implementing early prototypes of LAPPDs, high precision timing is possible. The suggested location for ANNIE is the SciBooNE hall on the Booster Neutrino Beam associated with the MiniBooNE experiment. The neutrino beam originates in Fermilab where The Booster delivers 8 GeV protons to a beryllium target producing secondary pions and kaons. These secondary mesons decay to produce a neutrino beam with an average energy of around 800 MeV. ANNIE will begin installation in the summer of 2015. Phase I of ANNIE, mapping the neutron background, completed in 2017. The detector is being upgraded for full science operation which is expected to begin late 2018.
The STEREO experiment investigates the possible oscillation of neutrinos from a nuclear reactor into light so-called sterile neutrinos. It is located at the Institut Laue–Langevin (ILL) in Grenoble, France. The experiment started operating and taking data in November 2016.
An accelerator neutrino is a human-generated neutrino or antineutrino obtained using particle accelerators, in which beam of protons is accelerated and collided with a fixed target, producing mesons which then decay into neutrinos. Depending on the energy of the accelerated protons and whether mesons decay in flight or at rest it is possible to generate neutrinos of a different flavour, energy and angular distribution. Accelerator neutrinos are used to study neutrino interactions and neutrino oscillations taking advantage of high intensity of neutrino beams, as well as a possibility to control and understand their type and kinematic properties to a much greater extent than for neutrinos from other sources.
Jocelyn Monroe is an American experimental particle physicist who is a Professor at Royal Holloway, University of London. Her research considers the development of novel detectors as part of the search for dark matter. In 2016 she was honoured with the Breakthrough Prize in Fundamental Physics for her work on the Sudbury Neutrino Observatory.
Geralyn P. (Sam) Zeller is an American neutrino physicist at Fermilab. At Fermilab, she is a participant in the MiniBooNE experiment, co-spokesperson for the MicroBooNE experiment, and deputy head of the Neutrino Division.
References
- ↑ "Resolution of puzzles from the LSND, KARMEN, and MiniBooNE experiments". Phys. Rev. D. 83: 015015. 28 January 2011. arXiv: 1009.5536 . Bibcode:2011PhRvD..83a5015G. doi:10.1103/PhysRevD.83.015015.
