A tetraquark,
in particle physics, is an exotic meson composed of four valence quarks. In
principle, a tetraquark state may be allowed in quantum chromodynamics, the
modern theory of strong interactions. Any established tetraquark state would be
an example of an exotic hadron which lies outside the quark model
classification.
In 2003 a particle temporarily called X(3872), by the Belle experiment inJapan
In 2004, the DsJ(2632) state seen in Fermilab's SELEX was suggested as a possible tetraquark candidate.
In 2007, Belle announced the observation of the Z(4430) state, a ccdu tetraquark candidate. There are also indications that the Y(4660), also discovered by Belle in 2007, could be a tetraquark state.
In 2009, Fermilab announced that they have discovered a particle temporarily called Y(4140), which may also be a tetraquark.
In 2010, two physicists from DESY and a physicist fromQuaid-i-Azam
University
ϒ(5S) meson (a form of bottomonium), a well-defined tetraquark resonance exists.
In June 2013, the BES III experiment inChina and the
Belle experiment in Japan
In 2014, the Large Hadron Collider experiment LHCb confirmed the existence of the Z(4430) state with a significance of over 13.9 σ.
In February 2016, the DØ experiment announced the observation of a narrow tetraquark candidate, named X(5568), decaying to Bsπ±. However, preliminary results from LHCb, presented at the 51st Rencontres de Moriond Electroweak session, show no evidence for the state, despite a much larger sample of B0sπ± candidates.
In June 2016, LHCb announced the discovery of three additional tetraquark candidates, called X(4274), X(4500) and X(4700).
In 2003 a particle temporarily called X(3872), by the Belle experiment in
In 2004, the DsJ(2632) state seen in Fermilab's SELEX was suggested as a possible tetraquark candidate.
In 2007, Belle announced the observation of the Z(4430) state, a ccdu tetraquark candidate. There are also indications that the Y(4660), also discovered by Belle in 2007, could be a tetraquark state.
In 2009, Fermilab announced that they have discovered a particle temporarily called Y(4140), which may also be a tetraquark.
In 2010, two physicists from DESY and a physicist from
ϒ(5S) meson (a form of bottomonium), a well-defined tetraquark resonance exists.
In June 2013, the BES III experiment in
In 2014, the Large Hadron Collider experiment LHCb confirmed the existence of the Z(4430) state with a significance of over 13.9 σ.
In February 2016, the DØ experiment announced the observation of a narrow tetraquark candidate, named X(5568), decaying to Bsπ±. However, preliminary results from LHCb, presented at the 51st Rencontres de Moriond Electroweak session, show no evidence for the state, despite a much larger sample of B0sπ± candidates.
In June 2016, LHCb announced the discovery of three additional tetraquark candidates, called X(4274), X(4500) and X(4700).
Afterword
See also this Newsweek article on recent work:
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