The X(3872) is an
exotic meson candidate with a mass of 3871.68 MeV/c
2 which does not fit into the
quark model
In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the E ...
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 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) di ...
or a
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–diquar ...
-antidiquark pair (
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 examp ...
).
The quantum numbers of X(3872) have been determined by the
LHCb experiment at
CERN
The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...
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
CMS may refer to:
Computing
* Call management system
* CMS-2 (programming language), used by the United States Navy
* Code Morphing Software, a technology used by Transmeta
* Collection management system for a museum collection
* Color managem ...
at CERN in January 2022.
[
]
See also
*
Meson
*
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 ...
*
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 bill ...
*
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 ...
*
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 ...
Notes
References
*
Mesons
Subatomic particles with spin 1
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