Four-quark exotic mesons

Abstract

We review our investigations devoted to the analysis of the resonances Zc(3900), Zc(4430), Zc(4100),X(4140), X(4274), a1(1420), Y (4660), X(2100), X(2239), and Y (2175) discovered in various processes by Belle,BaBar, BESIII, D0, CDF, CMS, LHCb and COMPASS collaborations. These resonances are considered as seriouscandidates to four-quark (tetraquark) exotic mesons. We treat all of them as diquark-antidiquark states with relevantspin-parities, find their masses and couplings, as well as explore their dominant strong decay channels. Calculationsare performed in the context of the QCD sum rule method. Thus, the spectroscopic parameters of the tetraquarksare evaluated using the two-point sum rules. For computations of the strong couplings GTM1M2 , corresponding tothe vertices TM1M2 and necessary to find the partial widths of the strong decays T → M1M2 , we employ either thethree-point or full/approximate versions of the QCD light-cone sum rules methods. Obtained results are compared withavailable experimental data, and with predictions of other theoretical studies.