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Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combination of protons and neutrons is called nuclear physics.
A quark is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly observable matter is composed of up quarks, down quarks and electrons. Owing to a phenomenon known as color confinement, quarks are never found in isolation; they can be found only within hadrons, which include baryons and mesons, or in quark–gluon plasmas. For this reason, much of what is known about quarks has been drawn from observations of hadrons.
In theoretical physics, quantum chromodynamics (QCD) is the study of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type of quantum field theory called a non-abelian gauge theory, with symmetry group SU(3). The QCD analog of electric charge is a property called color. Gluons are the force carriers of the theory, just as photons are for the electromagnetic force in quantum electrodynamics. The theory is an important part of the Standard Model of particle physics. A large body of experimental evidence for QCD has been gathered over the years.
The Standard Model of particle physics is the theory describing three of the four known fundamental forces in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.
In physics, a subatomic particle is a particle smaller than an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles, or an elementary particle, which is not composed of other particles. Particle physics and nuclear physics study these particles and how they interact. Most force-carrying particles like photons or gluons are called bosons and, although they have quanta of energy, do not have rest mass or discrete diameters and are unlike the former particles that have rest mass and cannot overlap or combine which are called fermions. The W and Z bosons, however, are an exception to this rule and have relatively large rest masses at approximately 80GeV and 90GeV respectively.
The charm quark, charmed quark, or c quark is an elementary particle found in composite subatomic particles called hadrons such as the J/psi meson and the charmed baryons created in particle accelerator collisions. Several bosons, including the W and Z bosons and the Higgs boson, can decay into charm quarks. All charm quarks carry charm, a quantum number. This second-generation particle is the third-most-massive quark, with a mass of 1.27±0.02 GeV/c2 as measured in 2022, and a charge of +2/3 e.
In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as where is the number of quarks, and is the number of antiquarks. Baryons have a baryon number of +1, mesons have a baryon number of 0, and antibaryons have a baryon number of −1. Exotic hadrons like pentaquarks and tetraquarks are also classified as baryons and mesons depending on their baryon number.
In particle physics, strangeness is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic interactions that occur in a short period of time. The strangeness of a particle is defined as: where n
s
represents the number of strange quarks and n
s
represents the number of strange antiquarks. Evaluation of strangeness production has become an important tool in search, discovery, observation and interpretation of quark–gluon plasma (QGP). Strangeness is an excited state of matter and its decay is governed by CKM mixing.
In physical cosmology, baryogenesis is the physical process that is hypothesized to have taken place during the early universe to produce baryonic asymmetry, i.e. the imbalance of matter (baryons) and antimatter (antibaryons) in the observed universe.
In particle physics, a glueball is a hypothetical composite particle. It consists solely of gluon particles, without valence quarks. Such a state is possible because gluons carry color charge and experience the strong interaction between themselves. Glueballs are extremely difficult to identify in particle accelerators, because they mix with ordinary meson states. In pure gauge theory, glueballs are the only states of the spectrum and some of them are stable.
The
J/ψ
(J/psi) meson is a subatomic particle, a flavor-neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as "charmonium" or psions. The
J/ψ
is the most common form of charmonium, due to its spin of 1 and its low rest mass. The
J/ψ
has a rest mass of 3.0969 GeV/c2, just above that of the
η
c, and a mean lifetime of 7.2×10−21 s. This lifetime was about a thousand times longer than expected.
In particle physics, lepton number is a conserved quantum number representing the difference between the number of leptons and the number of antileptons in an elementary particle reaction. Lepton number is an additive quantum number, so its sum is preserved in interactions. The lepton number is defined by where
In particle physics, preons are hypothetical point particles, conceived of as sub-components of quarks and leptons. 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 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 six preons, and quarks and leptons have only three.
In particle physics, flavour or flavor refers to the species of an elementary particle. The Standard Model counts six flavours of quarks and six flavours of leptons. They are conventionally parameterized with flavour quantum numbers that are assigned to all subatomic particles. They can also be described by some of the family symmetries proposed for the quark-lepton generations.
Christopher T. Hill is an American theoretical physicist at the Fermi National Accelerator Laboratory who did undergraduate work in physics at M.I.T., and graduate work at Caltech. Hill's Ph.D. thesis, "Higgs Scalars and the Nonleptonic Weak Interactions" (1977) contains one of the first detailed discussions of the two-Higgs-doublet model and its impact upon weak interactions. His work mainly focuses on new physics that can be probed in laboratory experiments or cosmology.
Shoichi Sakata was a Japanese physicist and Marxist who was internationally known for theoretical work on the subatomic particles. He proposed the two meson theory, the Sakata model, and the Pontecorvo–Maki–Nakagawa–Sakata neutrino mixing matrix.
Harald Fritzsch was a German theoretical physicist known for his contributions to the theory of quarks, the development of Quantum Chromodynamics and the grand unification of the standard model of particle physics.
Within the Schwinger-Dyson equation approach to calculate structure of bound states under quantum field theory dynamics, one applies truncation schemes such that the finite tower of integral equations for Green's functions becomes manageable. For hadrons as relativistic bound states of quarks and gluons interacting via the strong nuclear force, a well-adopted scheme is the rainbow-ladder truncation. Particularly the bound state amplitude of mesons is determined from the homogeneous Bethe-Salpeter equation. While the amplitude for baryons is solved from the Faddeev equation. Information on the structure of hadrons is contained within these amplitudes. The established quantum field theory of the strong interaction is quantum chromodynamics (QCD). The Maris-Tandy model is a practical case of the rainbow-ladder truncation that yields reasonable description for hadrons with up quarks, down quarks, and strange quarks as their valence quarks.
References
- ↑ P. Minkowski (1977). "μ --> e γ at a rate of one out of 109 muon decays?". Physics Letters B. 67 (4): 421–428. Bibcode:1977PhLB...67..421M. doi:10.1016/0370-2693(77)90435-X.
- 1 2 Fritzsch, H.; Minkowski, P. (1975). "Unified interactions of leptons and hadrons". Annals of Physics. 93 (1–2): 193–266. doi:10.1016/0003-4916(75)90211-0.
- ↑ Universität Bern – Albert Einstein Center for Fundamental Physics Archived 2013-09-30 at the Wayback Machine
- ↑ Properties of Hadron States Containing a Condensed Phase of Quark- Antiquark Excitations, Nucl. Phys, 57B (1973) 557
- ↑ On the Anomalous Divergence of the Dilatation Current in Gauge Theories, Bern University preprint, unpublished
- ↑ Minkowski, Peter; Kabana, Sonia (2014). "Oscillatory modes of quarks in baryons for 3 quark flavors u,d,s: Tuning to harmonic numbers of oscimodes of baryons". EPJ Web of Conferences. 71: 00090. doi: 10.1051/epjconf/20147100090 .
- ↑ On the Spontaneous Origin of Newton's Constant, Phys. Letters 71B (1978) 419
- ↑ On the Cosmological Equations in the Presence of a Spatially Homogeneous Torsion Field, Phys. Letters 173B (1986) 247 Letters, 85B (1979) 231
- ↑ with H. Fritzsch, ψ - Resonances, Gluons and the Zweig Rule, Nuovo Cimento 30A (1975) 393
- ↑ The Structure of SU(2)L × U(1) Weak Interactions Revisited, in Proceedings of the Int. School of Physics, Enrico Fermi, Course LXXXI, Theory of Fundamental Interactions, G. Costa and R. Gatto editors, 1982, p. 96
- ↑ with C. Greub, Calculation of Lepton Spectra from W-Production at the - Collider, in Proceedings of the First. Int. Symposium on the Fourth Family of Quarks and Leptons, 1987, D. B. Cline and A. Soni editors, Annals of the New York Acad. of Sciences, Vol. 518, 1987, p.50
- ↑ with A. Halprin, H. Primakoff and S.P. Rosen, Double-Beta Decay and a Massive Majorana Neutrino, Phys, Ref. D13 (1976) 2567
- ↑ with R.J. Crewther and J. Finjord, The Annihilation Process → γ γ with Massive Neutrinos in Cosmology, Nucl. Phys. B207 (1982) 269
- On the Anomalous Divergence of the Dilatation Current in Gauge Theories, Bern University preprint Sep 1976 - 16 pages, PRINT-76-0813 (BERN), unpublished, KEK scanned document: dated 1976-12.-12.a
