NUMI Off-Axis ve Appearance: The Neutrino
The neutrino (Italian for "little neutral one") is an elementary particle. The elementary particles, to our knowledge, are not composed of smaller particles. Neutrinos belong to the group of elementary particles known as leptons. The leptons are divided into two classes: charged and uncharged. You are likely familiar with the electron, which is a charged lepton.
Neutrinos are uncharged leptons, they are produced by natural radioactive decay and can be produced through particle acceleration in a laboratory setting. Neutrinos have very little mass, and travel very close to the speed of light. As such, they are able to pass through most matter without being affected. Most of the neutrinos that are created in the NuMI beam will arrive at the Far Detector within a fraction of a second.
Neutrinos come in at least three different 'flavors,' that is to say three different types. The electron neutrino is paired with light electron; the muon neutrino is paired with the electron's sibling the muon, and similarly for the heavy short-lived tau particle and tau neutrino. Quantum Mechanics (the physics of particles) predicts that neutrinos will change from one type to another, or oscillate, if they have mass.
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