Physicists from the LHCb collaboration have discovered a new tetraquark consisting of two charmed quarks and charmed the two recorded the creation. This is the first particle, where the interaction of gluon associated pair diquark and antidiquark. The results were presented at the workshop of the CERN-LHC.
According to the quark model of strongly interacting particles — hadrons — either form a pair of quark-antiquark (mesons), or collected in groups of three quarks (baryons: the neutron and the proton). The remaining particles are considered to be exotic, although in 1964 Murray Gell-Mann admits the possibility of the formation of larger particles by embedding a pair of quark-antiquark in the structure of the baryon or meson.
Only in 2014, physicists working on the LHCb detector, discovered a new particle Z(4430)+, consisting of 4 quarks: ccdu (C — charmed d — lower, u — upper). And in 2015 during the decay Λb0→ J/ψpK- physics after analysis of the results of the first run found two pentaquark J/ψp, and a year ago they presented the results of the analysis for the second run of the Collider operation — according to new data in this process are formed three pentaquark. About how to find tetraquark, we wrote four years ago in a material “Tetraquark is the Wild West”.
There are several areas to search for exotic particles: a light system (contain quarks u,d,s), light-heavy system (contain at least one b or c quark), and then double-heavy system (containing a pair of quark-antiquark c – or b-quarks). The latter is experimentally easier to detect, because their spectra are narrow and do not overlap with each other, and due to the large mass of particles they are described by models of quantum chromodynamics the non-relativistic theory.