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In particle physics, a hadron is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the electric force. Most of the mass of ordinary matter comes from two hadrons: the proton and the neutron, while most of the mass of the protons and neutrons is in turn due to the binding energy of their constituent quarks, due to the strong force.
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.
The omega baryons are a family of subatomic hadron particles that are represented by the symbol
Ω
and are either neutral or have a +2, +1 or −1 elementary charge. They are baryons containing no up or down quarks. Omega baryons containing top quarks are not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s, which is about a twentieth of the timescale for strong interactions, and therefore that they do not form hadrons.
The top quark, sometimes also referred to as the truth quark, is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs Boson. This coupling is very close to unity; in the Standard Model of particle physics, it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the CDF and DØ experiments at Fermilab.
A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them.
In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as
In particle physics, a kaon, also called a K meson and denoted
K
, is any of a group of four mesons distinguished by a quantum number called strangeness. In the quark model they are understood to be bound states of a strange quark and an up or down antiquark.
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.
A tetraquark, in particle physics, is an exotic meson composed of four valence quarks. A tetraquark state has long been suspected to be allowed by quantum chromodynamics, the modern theory of strong interactions. A tetraquark state is an example of an exotic hadron which lies outside the conventional quark model classification. A number of different types of tetraquark have been observed.
In particle physics, quarkonium is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle.
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.
The DØ experiment was a worldwide collaboration of scientists conducting research on the fundamental nature of matter. DØ was one of two major experiments located at the Tevatron Collider at Fermilab in Batavia, Illinois. The Tevatron was the world's highest-energy accelerator from 1983 until 2009, when its energy was surpassed by the Large Hadron Collider. The DØ experiment stopped taking data in 2011, when the Tevatron shut down, but data analysis is still ongoing. The DØ detector is preserved in Fermilab's DØ Assembly Building as part of a historical exhibit for public tours.
The Xi baryons or cascade particles are a family of subatomic hadron particles which have the symbol Ξ and may have an electric charge of +2 e, +1 e, 0, or −1 e, where e is the elementary charge.
Neutral B meson oscillations are one of the manifestations of the neutral particle oscillation, a fundamental prediction of the Standard Model of particle physics. It is the phenomenon of B mesons changing between their matter and antimatter forms before their decay. The
B
s meson can exist as either a bound state of a strange antiquark and a bottom quark, or a strange quark and bottom antiquark. The oscillations in the neutral B sector are analogous to the phenomena that produce long and short-lived neutral kaons.
The
B
s meson is a meson composed of a bottom antiquark and a strange quark. Its antiparticle is the
B
s meson, composed of a bottom quark and a strange antiquark.
The timeline of particle physics lists the sequence of particle physics theories and discoveries in chronological order. The most modern developments follow the scientific development of the discipline of particle physics.
The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called "F mesons" prior to 1986.
In particle physics, CP violation is a violation of CP-symmetry : the combination of C-symmetry and P-symmetry. CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C-symmetry) while its spatial coordinates are inverted. The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.
References
- ↑ "[no title cited]". repository.ubn.ru.nl. 2066/26242.
- ↑ Abulencia, A.; et al. (CDF Collaboration) (2006). "Observation of
B0
s–
B0
s Oscillations". Physical Review Letters . 97 (24): 242003. arXiv: hep-ex/0609040 . Bibcode:2006PhRvL..97x2003A. doi:10.1103/PhysRevLett.97.242003. PMID 17280271. - ↑ Abazov, V. M.; et al. (D0 Collaboration) (2006). "Direct Limits on the B0
s Oscillation Frequency" (PDF). Physical Review Letters . 97 (2): 021802. arXiv: hep-ex/0603029 . Bibcode:2006PhRvL..97b1802A. doi:10.1103/PhysRevLett.97.021802. hdl:10211.3/194397. PMID 16907434. S2CID 11632404. - ↑ "Fermilab's CDF scientists make it official: They have discovered the quick-change behavior of the B-sub-s meson, which switches between matter and antimatter 3 trillion times a second" (Press release). Fermilab. 25 September 2006. Retrieved 8 December 2007.
- ↑ Kotulak, R. (26 September 2006). "Antimatter discovery could alter physics: Particle tracked between real world, spooky realm". Deseret News . Archived from the original on 29 November 2007. Retrieved 8 December 2007.
- ↑ Overbye, D. (17 May 2010). "From Fermilab, a New Clue to Explain Human Existence?". The New York Times . Retrieved 26 December 2016.
- ↑ Timmer, J. (29 August 2011). "LHCb detector causes trouble for supersymmetry theory". Ars Technica . Retrieved 26 December 2012.
- ↑ CMS Collaboration; LHCb Collaboration (4 June 2015). "Observation of the rare B0
s → µ+ µ− decay from the combined analysis of CMS and LHCb data". Nature. 522 (7554): 68–72. arXiv: 1411.4413 . Bibcode:2015Natur.522...68C. doi:10.1038/nature14474. PMID 26047778. S2CID 4394036. - ↑ Aaij, R.; Beteta, C. Abellán; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J. (16 October 2015). "Search for the rare decays B0 → J/ψγ and B0
s → J/ψγ". Physical Review D. 92 (11): 112002. arXiv: 1510.04866 . Bibcode:2015PhRvD..92k2002A. doi:10.1103/PhysRevD.92.112002. S2CID 118320485. - ↑ Aaij, R.; et al. (21 February 2017). "Observation of the annihilation decay mode B0 → K+ K−". Physical Review Letters. 118 (8): 47–50. arXiv: 1610.08288 . Bibcode:2017PhRvL.118h1801A. doi:10.1103/PhysRevLett.118.081801. PMID 2828221. S2CID 27186492.
