CERN Told About The Discovery Of A New Tetraquark
Physicists of the LHCb project have discovered a new type of tetraquark, which consists of two charming quarks and two charming antiquarks. This discovery will help scientists better understand how quarks – components of protons, neutrons, and other elementary particles-bind together, writes the website of the European Organization for Nuclear Research (CERN) with reference to an article in the Electronic Scientific Library arXiv.
"Particles of four quarks are definitely exotic, and the one that we just discovered is the first one that consists of four heavy quarks of the same type: two charmed quarks and two charming antiquarks," said one of the LHCb participants, Giovanni Passaleva. – Previously, in the framework of LHCb and other experiments, we observed tetraquarks with only two heavy quarks, and never with more than two quarks of the same type."
According to the Standard Model, the theory that describes most of the interactions of all known elementary particles, there are three groups of particles: quarks, leptons, and gauge bosons. The atomic nuclei of all substances consist of quarks. They are held together by carriers of the strong interaction – gluons.
Each quark corresponds to its antipode – the antiquark. All quarks are divided into six types ("flavors") – upper, lower, strange, enchanted, true, and charming.
It was previously thought that elementary particles could consist of two or three quarks. Particles of one quark and one antiquark that are bound by gluons are called mesons. Three quarks make up baryons-protons and neutrons. However, over the past ten years, physicists, thanks to the work of colliders, have discovered particles that were considered exotic – tetraquarks and pentaquarks.
In the course of a new analysis of data obtained during the first two runs of the Large hadron Collider, physicists from the LHCb project came across traces of the existence of another new type of tetraquark. According to scientists, gluons in it connect pairs of charmed quarks and charmed antiquarks.
However, scientists do not yet fully understand, as in the case of previously discovered tetraquarks, whether the new particle is a "genuine tetraquark", that is, a system of strongly connected quarks, or a pair of two-quark particles that form a kind of molecule due to the weak interaction. However, in any case, the new tetraquark will help theorists test models of quantum chromodynamics – the theory of quantum fields that describes the strong interaction of elementary particles, CERN believes.