The X(3872) is an
exotic meson
In particle physics, 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: ...
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 that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the Eig ...
. It was first discovered in 2003 by the
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, Ibara ...
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 ...
or a
diquark-antidiquark pair (
tetraquark
In particle physics, a tetraquark 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 ...
).
The quantum numbers of X(3872) have been determined by the
LHCb
The LHCb (Large Hadron Collider beauty) experiment is a particle physics detector collecting data at the Large Hadron Collider at CERN. LHCb specializes in the measurements of the parameters of CP violation in the interactions of b- and c-hadro ...
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 Meyrin, western 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
Quark–gluon plasma (QGP or quark soup) is an interacting localized assembly of quarks and gluons at Thermodynamic equilibrium#Local and global equilibrium, thermal (local kinetic) and (close to) chemical (abundance) equilibrium. The word ''plasm ...
have been reported by the
CMS experiment at CERN in January 2022.
[
]
See also
*
Meson
In particle physics, a meson () 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, the ...
*
XYZ particle
*
Y(4140)
*
Z(4430)
Z(4430) is a mesonic resonance
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a ...
*
Zc(3900)
Notes
References
*
Mesons
Subatomic particles with spin 1
{{particle-stub