Abstract

We present a study of the isospin-violating one-pion strong decays of single heavy tetraquarks X-Q = X(sq (q) over bar(Q) over bar), Q = c, b, and q = u, d with spin-parity J(P) = 0(+). We assume that the tetraquarks have the configuration of a color diquark and an antidiquark. Three mechanisms of isospin violation can contribute to the decay rate: (1) mixing of the X(su (u) over bar(Q) over bar) and X(sd (d) over bar(Q) over bar) tetraquark currents, (2) an explicit m(d) - m(u) quark mass difference in the quark diagrams describing the corresponding decay transitions, and (3) pi(0) - eta mixing in the final state. Our main results are as follows: (1) It is quite likely that the investigated tetraquark states are isosinglet states with a small admixture of an isotriplet component; (2) The first isospin-breaking mechanism affects the decay rather more significantly than the others; (3) Our calculations contain a size parameter Lambda(XQ), characterizing the distribution of the quarks in the tetraquark state X-Q. Absolute decay rates depend very much on the choice of Lambda(XQ), varied from 1 to 2 GeV, reflecting the compactness of the multiquark system.