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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 due to the very small mass of the neutrino, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.
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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, ordinary active neutrinos in the Standard Model, which carry an isospin charge of ±+1/ 2 and engage in the weak interaction. The term typically refers to neutrinos with right-handed chirality, which may be inserted into 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).
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References
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- ↑ Boyarsky, A.; Ruchayskiy, O.; Iakubovskyi, D.; Franse, J. (2014-12-15). "Unidentified Line in X-Ray Spectra of the Andromeda Galaxy and Perseus Galaxy Cluster". Physical Review Letters. 113 (25): 251301. arXiv: 1402.4119 . Bibcode:2014PhRvL.113y1301B. doi:10.1103/physrevlett.113.251301. ISSN 0031-9007. PMID 25554871. S2CID 21406370.
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