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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.
Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories. Neutrinos are created as a result of certain types of radioactive decay, nuclear reactions such as those that take place in the Sun or high energy astrophysical phenomena, in nuclear reactors, or when cosmic rays hit atoms in the atmosphere. Neutrinos rarely interact with matter, meaning that it is unlikely for them to scatter along their trajectory, unlike photons. Therefore, neutrinos offer a unique opportunity to observe processes that are inaccessible to optical telescopes, such as reactions in the Sun's core. Neutrinos can also offer a very strong pointing direction compared to charged particle cosmic rays.
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.
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In particle physics, the parton model is a model of hadrons, such as protons and neutrons, proposed by Richard Feynman. It is useful for interpreting the cascades of radiation produced from quantum chromodynamics (QCD) processes and interactions in high-energy particle collisions.
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A neutrino detector is a physics apparatus which is designed to study neutrinos. Because neutrinos only weakly interact with other particles of matter, neutrino detectors must be very large to detect a significant number of neutrinos. Neutrino detectors are often built underground, to isolate the detector from cosmic rays and other background radiation. The field of neutrino astronomy is still very much in its infancy – the only confirmed extraterrestrial sources as of 2018 are the Sun and the supernova 1987A in the nearby Large Magellanic Cloud. Another likely source is the blazar TXS 0506+056 about 3.7 billion light years away. Neutrino observatories will "give astronomers fresh eyes with which to study the universe".
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The LHCf is a special-purpose Large Hadron Collider experiment for astroparticle physics, and one of nine detectors in the LHC accelerator at CERN. LHCf is designed to study the particles generated in the forward region of collisions, those almost directly in line with the colliding proton beams.
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KASCADE was a European physics experiment started in 1996 at Forschungszentrum Karlsruhe, Germany, an extensive air shower experiment array to study the cosmic ray primary composition and the hadronic interactions, measuring simultaneously the electronic, muonic and hadronic components.
UrQMD is a fully integrated Monte Carlo simulation package for Proton+Proton, Proton+nucleus and nucleus+nucleus interactions. UrQMD has many applications in particle physics, high energy experimental physics and engineering, shielding, detector design, cosmic ray studies, and medical physics.
The High Altitude Water Cherenkov Experiment or High Altitude Water Cherenkov Observatory is a gamma-ray and cosmic ray observatory located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters, at 18°59′41″N97°18′30.6″W. HAWC is the successor to the Milagro gamma-ray observatory in New Mexico, which was also a gamma-ray observatory based around the principle of detecting gamma-rays indirectly using the water Cherenkov method.
The Giant Radio Array for Neutrino Detection (GRAND) is a proposed large-scale detector designed to collect ultra-high energy cosmic particles as cosmic rays, neutrinos and photons with energies exceeding 1017 eV. This project aims at solving the mystery of their origin and the early stages of the universe itself. The proposal, formulated by an international group of researchers, calls for an array of 200,000 receivers to be placed on mountain ranges around the world.
The Waxman-Bahcall bound is a computed upper limit on the observed flux of high energy neutrinos based on the observed flux of high energy cosmic rays. Since the highest energy neutrinos are produced in the same interactions as high energy cosmic rays, the observed rate of production of the latter places a limit on the former. It is named for John Bahcall and Eli Waxman.
References
- ↑ Pierog, Tanguy; Heck, Dieter; Ulrich, Ralf. "CORSIKA". Zenodo. doi:10.5281/zenodo.5246070.
- ↑ Pierog, Tanguy; Werner, Klaus (2009). "EPOS Model and Ultra High Energy Cosmic Rays". Nucl. Phys. B Proc. Suppl. 196: 102–205. arXiv: 0905.1198 . doi:10.1016/j.nuclphysbps.2009.09.017.
- ↑ Huege, T.; Ludwig, M.; James, C. W. (2013). "Simulating radio emission from air showers with CoREAS". AIP Conf. Proc. 1535 (1): 128. arXiv: 1301.2132 . doi:10.1063/1.4807534.
- ↑ Engel, Ralph; et al. (2019). "Towards a next generation of CORSIKA: A framework for the simulation of particle cascades in astroparticle physics". Comput. Softw. Big Sci. 3: 2. arXiv: 1808.08226 . doi:10.1007/s41781-018-0013-0.
