Neutrino oscillation is a quantum mechanical phenomenon in which a neutrinocreated with a specific lepton family number ("lepton flavor": electron, muon, or tau) 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.[1]
First predicted by Bruno Pontecorvo in 1957,[2][3] neutrino oscillation has since been observed by a multitude of experiments in several different contexts. Most notably, the existence of neutrino oscillation resolved the long-standing solar neutrino problem.
Neutrino oscillation is of great theoretical and experimental interest, as the precise properties of the process can shed light on several properties of the neutrino. In particular, it implies that the neutrino has a non-zero mass, which requires a modification to the Standard Model of particle physics.[1] The experimental discovery of neutrino oscillation, and thus neutrino mass, by the Super-Kamiokande Observatoryand the Sudbury Neutrino Observatories was recognized with the 2015 Nobel Prize for Physics.[4]
https://en.wikipedia.org/wiki/Neutrino_oscillation
Wednesday, September 15, 2021
09-15-2021-0441 - Preons Preon
In particle physics, preons are point particles, conceived of as sub-components of quarks and leptons.[1] The word was coined by Jogesh Pati and Abdus Salam, in 1974. Interest in preon models peaked in the 1980s but has slowed, as the Standard Model of particle physics continues to describe the physics, mostly successfully, and no direct experimental evidence for lepton and quark compositeness has been found. Preons come in four varieties, plus, anti-plus, zero and anti-zero. W bosons have 6 preons and quarks have only 3.
In the hadronic sector, some effects are considered anomalies within the Standard Model. For example, the proton spin puzzle, the EMC effect, the distributions of electric charges inside the nucleons, as found by Hofstadter in 1956,[2][3] and the ad hoc CKM matrixelements.
When the term "preon" was coined, it was primarily to explain the two families of spin-½ fermions: quarks and leptons. More recent preon models also account for spin-1 bosons, and are still called "preons". Each of the preon models postulates a set of fewer fundamental particles than those of the Standard Model, together with the rules governing how those fundamental particles combine and interact. Based on these rules, the preon models try to explain the Standard Model, often predicting small discrepancies with this model and generating new particles and certain phenomena, which do not belong to the Standard Model.
https://en.wikipedia.org/wiki/Preon
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