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X(3872)
The X(3872) is an exotic meson candidate with a mass of 3871.68 MeV/c2 which does not fit into the quark model because of its quantum numbers. It was first discovered in 2003 by the Belle experiment in Japan and later confirmed by several other experimental collaborations. Several theories have been proposed for its nature, such as a mesonic molecule or a diquark-antidiquark pair ( tetraquark). The quantum numbers of X(3872) have been determined by the LHCb experiment at CERN in March 2013. The values for J P C are 1++. The first evidence of X(3872) production in the quark–gluon plasma have been reported by the CMS experiment at CERN in January 2022. See also * Meson In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, ... * XYZ particle * Y(4140) * Z(4430) * Zc(3900) Notes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XYZ Particle
XYZ particles, also referred to as XYZ states, are recently discovered heavy mesons whose properties do not appear to fit the standard picture of charmonium and bottomonium states. They are therefore types of exotic meson. The term arises from the names given to some of the first such particles discovered: X(3872), Y(4260) and Zc(3900), although the symbols X and Y have since been deprecated by the Particle Data Group. Theoretical significance Since 2003 a frontier for the Standard Model (SM) has emerged at low energies through XYZ particle discoveries. The well-established theory of Quantum Chromodynamics (QCD) is tested by many exotic charmonium discoveries since the X(3872) was first identified at the Belle experiment in 2003. The basic model of hadron physics is the assembling of quarks into groups of 3 (baryons) or a quark and anti-quark pair (mesons). A meson with a charm quark and an anti-charm quark is called ''charmonium'', and the same parallels with the bottom quark ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetraquark
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. History and discoveries Several tetraquark candidates have been reported by particle physics experiments in the 21st century. The quark contents of these states are almost all qQ, where q represents a light ( up, down or strange) quark, Q represents a heavy (charm or bottom) quark, and antiquarks are denoted with an overline. The existence and stability of tetraquark states with the qq (or QQ) have been discussed by theoretical physicists for a long time, however these are yet to be reported by experiments. ;Timeline In 2003, a particle temporarily called X(3872), by the Belle experiment in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Y(4140)
The Y(4140) particle is an electrically neutral exotic hadron candidate that is about 4.4 times heavier than the proton. It was observed at Fermilab and announced on 17 March 2009. This particle is extremely rare and was detected in only 20 of billions of collisions. Since it decays into J/ψ and φ mesons, it has been suggested that this particle is composed of charm quarks and charm antiquarks, possibly even a four quark combination. The existence of the particle has been confirmed by members of the CMS collaboration at the Large Hadron Collider on November 14, 2012 and by the DØ experiment at the Tevatron on September 25, 2013. The Belle experiment has searched for this particle but found no evidence for its existence. The LHCb experiment observes a peak at the same position in the J/ψϕ invariant mass, but it is best described as a Ds±Ds∗∓ cusp, and is much broader than the previous measurements of the Y(4140). The Particle Data Group has renamed Y(4140) to follow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LHCb Experiment
The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region. The LHCb collaboration, who built, operate and analyse data from the experiment, is composed of approximately 1260 people from 74 scientific institutes, representing 16 countries. Chris Parkes succeeded on July 1, 2020 as spokesperson for the collaboration to Giovanni Passaleva (spokesperson 2017-2020). The experiment is located at point 8 on the LHC tunnel close to Ferney-Voltaire, France just ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zc(3900)
The Zc(3900) is a hadron, a type of subatomic particle made of quarks, believed to be the first tetraquark that has been observed experimentally. The discovery was made in 2013 by two independent research groups: one using the BES III detector at the Chinese Beijing Electron Positron Collider, the other being part of the Belle experiment group at the Japanese KEK particle physics laboratory.. The Zc(3900) is a decay product of the previously observed anomalous Y(4260) particle. The Zc(3900) in turn decays into a charged pion (π±) and a J/ψ meson. This is consistent with the Zc(3900) containing four or more quarks. The first evidence of the neutral Zc(3900) was provided by CLEO-c in 2013. It was later observed by BESIII in 2015. It decays into a neutral pion (π0) and a J/ψ meson. Researchers were expected to run decay experiments in 2013 to determine the particle's nature with more precision. See also * XYZ particle * X(3872) * Y(4140) The Y(4140) particle is an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belle Experiment
The Belle experiment was a particle physics experiment conducted by the Belle Collaboration, an international collaboration of more than 400 physicists and engineers, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan. The experiment ran from 1999 to 2010. The Belle detector was located at the collision point of the asymmetric-energy electron–positron collider, KEKB. Belle at KEKB together with the BaBar experiment at the PEP-II accelerator at SLAC were known as the B-factories as they collided electrons with positrons at the center-of-momentum energy equal to the mass of the (4S) resonance which decays to pairs of B mesons. The Belle detector was a hermetic multilayer particle detector with large solid angle coverage, vertex location with precision on the order of tens of micrometres (provided by a silicon vertex detector), good distinction between pions and kaons in the momenta range from 100 MeV/c to few GeV/c (provided ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Z(4430)
Z(4430) is a mesonic resonance discovered by the Belle experiment. It has a mass of . The resonant nature of the peak has been confirmed by the LHCb experiment with a significance of at least 13.9 σ. The particle is charged and is thought to have a quark content of , making it a tetraquark candidate. It has the spin-parity quantum numbers J P = 1+. The particle joins the X(3872), Zc(3900) The Zc(3900) is a hadron, a type of subatomic particle made of quarks, believed to be the first tetraquark that has been observed experimentally. The discovery was made in 2013 by two independent research groups: one using the BES III detector a ... and Y(4140) as exotic hadron candidates observed by multiple experiments, although it is the first to be confirmed as a resonance. See also * XYZ particle References External links Major harvest of four-leaf clover Mesons 2014 in science Subatomic particles with spin 1 {{particle-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesonic Molecule
A mesonic molecule is a set of two or more mesons bound together by the strong force. Unlike baryonic molecules, which form the nuclei of all elements in nature save hydrogen-1, a mesonic molecule has yet to be definitively observed. The X(3872) discovered in 2003 and the Z(4430) discovered in 2007 by the Belle experiment are the best candidates for such an observation. See also *Meson *Tetraquark 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 ... * Pionium References Hypothetical composite particles {{Particle-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diquark
In particle physics, a diquark, or diquark correlation/clustering, is a hypothetical state of two quarks grouped inside a baryon (that consists of three quarks) (Lichtenberg 1982). Corresponding models of baryons are referred to as quark–diquark models. The diquark is often treated as a single subatomic particle with which the third quark interacts via the strong interaction. The existence of diquarks inside the nucleons is a disputed issue, but it helps to explain some nucleon properties and to reproduce experimental data sensitive to the nucleon structure. Diquark–antidiquark pairs have also been advanced for anomalous particles such as the X(3872). Formation The forces between the two quarks in a diquark is attractive when both the colors and spins are antisymmetric. When both quarks are correlated in this way they tend to form a very low energy configuration. This low energy configuration has become known as a diquark. Controversy Many scientists theorize that a diquar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LHCb
The LHCb (Large Hadron Collider beauty) experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region. The LHCb collaboration, who built, operate and analyse data from the experiment, is composed of approximately 1260 people from 74 scientific institutes, representing 16 countries. Chris Parkes succeeded on July 1, 2020 as spokesperson for the collaboration to Giovanni Passaleva (spokesperson 2017-2020). The experiment is located at point 8 on the LHC tunnel close to Ferney-Voltaire, France jus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exotic Meson
Exotic mesons are mesons that have quantum numbers not possible in the quark model; some proposals for non-standard quark model mesons could be: ; glueballs or gluonium: Glueballs have no valence quarks at all. ; tetraquarks: Tetraquarks have two valence quark–antiquark pairs. ;hybrid mesons: Hybrid mesons contain a valence quark–antiquark pair and one or more gluons. All exotic mesons are classed as mesons because they are hadrons and carry zero baryon number. Of these, glueballs must be flavor singlets – that is, must have zero isospin, strangeness, charm, bottomness, and topness. Like all particle states, exotic mesons are specified by the quantum numbers which label representations of the Poincaré symmetry, q.e., by the mass (enclosed in parentheses), and by , where is the angular momentum, is the intrinsic parity, and is the charge conjugation parity; One also often specifies the isospin of the meson. Typically, every quark model meson comes in SU(3) fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meson
In particle physics, a meson ( or ) is a type of hadronic subatomic particle composed of an equal number of quarks and antiquarks, usually one of each, bound together by the strong interaction. Because mesons are composed of quark subparticles, they have a meaningful physical size, a diameter of roughly one femtometre (10 m), which is about 0.6 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Heavier mesons decay to lighter mesons and ultimately to stable electrons, neutrinos and photons. Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high-energy protons and neutrons) and baryonic matter. Mesons are routinely produced artificially in cyclotrons or other particle accelerators in the collisions of protons, antiprotons, or other particles. Higher-energy (more massive) me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
