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A neutrino (/ nj uː ˈ t r iː n oʊ / new-TREE-noh; denoted by the Greek letter ν) is an elementary particle that interacts via the weak interaction and gravity. [2] [3] The neutrino is so named because it is electrically neutral and because its rest mass is so small that it was long thought to be zero.
In 1950, 30 charged and 4 neutral "V-particles" were reported. Inspired by this, numerous mountaintop observations were made over the next several years, and by 1953, the following terminology was being used: "L meson" for either a muon or charged pion; "K meson" meant a particle intermediate in mass between the pion and nucleon.
Other neutral particles are very short-lived and decay before they could be detected even if they were charged. They have been observed only indirectly. They include: Z bosons [PDG 4] Dozens of heavy neutral hadrons: Neutral mesons such as the π 0 [PDG 5] and K 0 [PDG 6] The neutral Delta baryon (Δ 0), [PDG 7] and other neutral baryons, such ...
On 4 July 2012, the discovery of a new particle with a mass between 125 and 127 GeV/c 2 was announced; physicists suspected that it was the Higgs boson. Since then, the particle has been shown to behave, interact, and decay in many of the ways predicted for Higgs particles by the Standard Model, as well as having even parity and zero spin, two ...
Couples to mass (i.e., strength of interaction with Standard Model particles proportional to their mass) Particle physicist Adam Falkowski states that the essential qualities of a Higgs boson are that it is a spin-0 (scalar) particle which also couples to mass (W and Z bosons); proving spin-0 alone is insufficient. [13]
In May 2024, the Particle Data Group estimated the World Average mass for the W boson to be 80369.2 ± 13.3 MeV, based on experiments to date. [ 11 ] As of 2021, experimental measurements of the W boson mass had been similarly assessed to converge around 80 379 ± 12 MeV , [ 12 ] all consistent with one another and with the Standard Model.
The lambda baryon Λ 0 was first discovered in October 1950, by V. D. Hopper and S. Biswas of the University of Melbourne, as a neutral V particle with a proton as a decay product, thus correctly distinguishing it as a baryon, rather than a meson, [2] i.e. different in kind from the K meson discovered in 1947 by Rochester and Butler; [3] they were produced by cosmic rays and detected in ...
The free neutron has a mass of 939 565 413.3 eV/c 2, or 939.565 4133 MeV/c 2. This mass is equal to 1.674 927 471 × 10 −27 kg, or 1.008 664 915 88 Da. [4] The neutron has a mean-square radius of about 0.8 × 10 −15 m, or 0.8 fm, [20] and it is a spin-½ fermion. [21] The neutron has no measurable electric charge.