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Super-Kamiokande is a neutrino observatory located under Mount Ikeno near the city of Hida, Gifu Prefecture, Japan. It is operated by the Institute for Cosmic Ray Research, University of Tokyo with the help of an international team. It is located 1,000 m (3,300 ft) underground in the Mozumi Mine in Hida's Kamioka area. The observatory was designed to detect high-energy neutrinos, to search for proton decay, study solar and atmospheric neutrinos, and keep watch for supernovae in the Milky Way Galaxy.
Cosmic rays or astroparticles are high-energy particles or clusters of particles that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own galaxy, and from distant galaxies. Upon impact with Earth's atmosphere, cosmic rays produce showers of secondary particles, some of which reach the surface, although the bulk are deflected off into space by the magnetosphere or the heliosphere.
The Greisen–Zatsepin–Kuzmin limit (GZK limit or GZK cutoff) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy. The limit is 5×1019 eV (50 EeV), or about 8 joules (the energy of a proton travelling at ≈ 99.99999999999999999998% the speed of light). The limit is set by the slowing effect of interactions of the protons with the microwave background radiation over long distances (≈ 160 million light-years). The limit is at the same order of magnitude as the upper limit for energy at which cosmic rays have experimentally been detected, although indeed some detections appear to have exceeded the limit, as noted below. For example, one extreme-energy cosmic ray, the Oh-My-God Particle, which has been found to possess a record-breaking 3.12×1020 eV (50 joules) of energy (about the same as the kinetic energy of a 95 km/h baseball).
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles.
Air showers are extensive cascades of subatomic particles and ionized nuclei, produced in the atmosphere when a primary cosmic ray enters the atmosphere. When a particle of the cosmic radiation, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, interacts with the nucleus of a molecule in the atmosphere, it produces a vast number of secondary particles, which make up the shower. In the first interactions of the cascade especially hadrons are produced and decay rapidly in the air, producing other particles and electromagnetic radiation, which are part of the shower components. Depending on the energy of the cosmic ray, the detectable size of the shower can reach several kilometers in diameter.
The High Resolution Fly's Eye or HiRes detector was an ultra-high-energy cosmic ray observatory that operated in the West Desert of Utah from May 1997 until April 2006. HiRes used the "atmospheric fluorescence" technique that was pioneered by the Utah group first in tests at the Volcano Ranch experiment and then with the original Fly's Eye experiment. The version HiRes-II followed later.
The Pierre Auger Observatory is an international cosmic ray observatory in Argentina designed to detect ultra-high-energy cosmic rays: sub-atomic particles traveling nearly at the speed of light and each with energies beyond 1018 eV. In Earth's atmosphere such particles interact with air nuclei and produce various other particles. These effect particles (called an "air shower") can be detected and measured. But since these high energy particles have an estimated arrival rate of just 1 per km2 per century, the Auger Observatory has created a detection area of 3,000 km2 (1,200 sq mi)—the size of Rhode Island, or Luxembourg—in order to record a large number of these events. It is located in the western Mendoza Province, Argentina, near the Andes.
The Haverah Park experiment was a cosmic ray air shower detection array consisting of water Cherenkov detectors distributed over an area of 12 km2 on Haverah Park on the Pennine moorland near Harrogate, North Yorkshire. The experiment was operated by University of Leeds for 20 years, and was switched off in 1987.
The Akeno Giant Air Shower Array (AGASA) was an array of particle detectors designed to study the origin of ultra-high-energy cosmic rays. It was deployed from 1987 to 1991 and decommissioned in 2004. It consisted of 111 scintillation detectors and 27 muon detectors spread over an area of 100 km2. It was operated by the Institute for Cosmic Ray Research, University of Tokyo at the Akeno Observatory.
VERITAS is a major ground-based gamma-ray observatory with an array of four 12 meter optical reflectors for gamma-ray astronomy in the GeV – TeV photon energy range. VERITAS uses the Imaging Atmospheric Cherenkov Telescope technique to observe gamma rays that cause particle showers in Earth's atmosphere that are known as extensive air showers. The VERITAS array is located at the Fred Lawrence Whipple Observatory, in southern Arizona, United States. The VERITAS reflector design is similar to the earlier Whipple 10-meter gamma-ray telescope, located at the same site, but is larger in size and has a longer focal length for better control of optical aberrations. VERITAS consists of an array of imaging telescopes deployed to view atmospheric Cherenkov showers from multiple locations to give the highest sensitivity in the 100 GeV – 10 TeV band. This very high energy observatory, completed in 2007, effectively complements the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope due to its larger collection area as well as coverage in a higher energy band.
Extragalactic cosmic rays are very-high-energy particles that flow into the Solar System from beyond the Milky Way galaxy. While at low energies, the majority of cosmic rays originate within the Galaxy (such as from supernova remnants), at high energies the cosmic ray spectrum is dominated by these extragalactic cosmic rays. The exact energy at which the transition from galactic to extragalactic cosmic rays occurs is not clear, but it is in the range 1017 to 1018 eV.
The Institute for Cosmic Ray Research (ICRR) of the University of Tokyo was established in 1976 for the study of cosmic rays.
The Telescope Array project is an international collaboration involving research and educational institutions in Japan, The United States, Russia, South Korea, and Belgium. The experiment is designed to observe air showers induced by ultra-high-energy cosmic ray using a combination of ground array and air-fluorescence techniques. It is located in the high desert in Millard County, Utah, United States, at about 1,400 meters (4,600 ft) above sea level.
A cosmic-ray observatory is a scientific installation built to detect high-energy-particles coming from space called cosmic rays. This typically includes photons, electrons, protons, and some heavier nuclei, as well as antimatter particles. About 90% of cosmic rays are protons, 9% are alpha particles, and the remaining ~1% are other particles.
John David Linsley (12 March 1925 – 15 September 2002) was an American physicist who performed pioneering research on cosmic rays, particularly ultra-high-energy cosmic rays. He did his most significant work from 1959 to 1978 using a ground-based array of detectors at Volcano Ranch in New Mexico. He is best known for being the first to detect an air shower created by a primary particle with an energy of 1020 eV. This was the highest energy cosmic ray observed up to that point. Linsley's observations suggested that not all cosmic rays are confined within the galaxy and showed the first evidence of a flattening of the cosmic ray spectrum at energies above 1018 eV.
Takaaki Kajita is a Japanese physicist, known for neutrino experiments at the Kamioka Observatory – Kamiokande and its successor, Super-Kamiokande. In 2015, he was awarded the Nobel Prize in Physics jointly with Canadian physicist Arthur B. McDonald. On 1 October 2020, he became the president of the Science Council of Japan.
XMASS is a multipurpose physics experiment in Japan that monitors a large tank of xenon for flashes of light that might be caused by hypothetical dark matter particles. In addition to searching for dark matter, XMASS is also studying neutrinoless double beta decay and solar neutrinos. The project is conducted by a team at Institute for Cosmic Ray Research, University of Tokyo.
Eugene Chen Loh was a Chinese American physicist, having been Distinguished Professor Emeritus at University of Utah and was a Fellow of the American Physical Society.
Francis Louis Halzen is a Belgian particle physicist. He is the Hilldale and Gregory Breit Distinguished Professor at the University of Wisconsin–Madison and Director of its Institute for Elementary Particle Physics. Halzen is the Principal Investigator of the IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station in Antarctica, the world's largest neutrino detector which has been operational since 2010.
The Large High Altitude Air Shower Observatory (LHAASO) is a gamma-ray and cosmic-ray observatory in Daocheng, in the Garzê Tibetan Autonomous Prefecture in Sichuan, China. It is designed to observe air showers triggered by gamma rays and cosmic rays. The observatory is at an altitude of 4,410 metres (14,470 ft) above sea level. Observations started in April 2019.
References
- ↑ "Akeno Observatory / About ICRR". www.icrr.u-tokyo.ac.jp.
- ↑ "AGASA (Akeno Giant Air Shower Array)". www-akeno.icrr.u-tokyo.ac.jp.
- ↑ "History / About ICRR". www.icrr.u-tokyo.ac.jp.
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