Subatomic particles in the context of Wave–particle duality

In nuclear physics and particle physics, the weak interaction, weak force or the weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, and gravitation. It is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms: The weak interaction participates in nuclear fission and nuclear fusion. The theory describing its behaviour and effects is sometimes called quantum flavordynamics (QFD); however, the term QFD is rarely used, because the weak force is better understood by electroweak theory (EWT).

The effective range of the weak force is limited to subatomic distances and is less than the diameter of a proton.

Exotic hadrons are subatomic particles composed of quarks and gluons, but which – unlike "well-known" hadrons such as protons, neutrons and mesons – consist of more than three valence quarks. By contrast, "ordinary" hadrons contain just two or three quarks. Hadrons with explicit valence gluon content would also be considered exotic. In theory, there is no limit on the number of quarks in a hadron, as long as the hadron's color charge is white, or color-neutral.

Consistent with ordinary hadrons, exotic hadrons are classified as being either fermions, like ordinary baryons, or bosons, like ordinary mesons. According to this classification scheme, pentaquarks, containing five valence quarks, are exotic baryons, while tetraquarks (four valence quarks) and hexaquarks (six quarks, consisting of either a dibaryon or three quark-antiquark pairs) would be considered exotic mesons. Tetraquark and pentaquark particles are believed to have been observed and are being investigated; hexaquarks have not yet been confirmed as observed.

A spectrometer (/spɛkˈtrɒmɪtər/) is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the spectral components are somehow mixed. In visible light a spectrometer can separate white light and measure individual narrow bands of color, called a spectrum. A mass spectrometer measures the spectrum of the masses of the atoms or molecules present in a gas. The first spectrometers were used to split light into an array of separate colors. Spectrometers were developed in early studies of physics, astronomy, and chemistry. The capability of spectroscopy to determine chemical composition drove its advancement and continues to be one of its primary uses. Spectrometers are used in astronomy to analyze the chemical composition of stars and planets, and spectrometers gather data on the origin of the universe.

Examples of spectrometers are devices that separate particles, atoms, and molecules by their mass, momentum, or energy. These types of spectrometers are used in chemical analysis and particle physics.

In nuclear and particle physics, a geoneutrino is a neutrino or antineutrino emitted during the decay of naturally occurring radionuclides in the Earth. Neutrinos, the lightest of the known subatomic particles, lack measurable electromagnetic properties and interact only via the weak nuclear force (when ignoring gravity). Matter is virtually transparent to neutrinos and consequently they travel, unimpeded, at near light speed through the Earth from their point of emission. Collectively, geoneutrinos carry integrated information about the abundances of their radioactive sources inside the Earth. A major objective of the emerging field of neutrino geophysics involves extracting geologically useful information (e.g., abundances of individual geoneutrino-producing elements and their spatial distribution in Earth's interior) from geoneutrino measurements. Analysts from the Borexino collaboration have been able to get to 53 events of neutrinos originating from the interior of the Earth.

Most geoneutrinos are electron antineutrinos originating in β
decay branches of K, Th and U. Together these decay chains account for more than 99% of the present-day radiogenic heat generated inside the Earth. Only geoneutrinos from Th and U decay chains are detectable by the inverse beta-decay mechanism on the free proton because these have energies above the corresponding threshold (1.8 MeV). In neutrino experiments, large underground liquid scintillator detectors record the flashes of light generated from this interaction. As of 2016 geoneutrino measurements at two sites, as reported by the KamLAND and Borexino collaborations, have begun to place constraints on the amount of radiogenic heating in the Earth's interior. A third detector (SNO+) is expected to start collecting data in 2017. JUNO experiment is under construction in Southern China. Another geoneutrino detecting experiment is planned at the China Jinping Underground Laboratory.