The mechanism of channel coupling via decay products is used to study energy shifts, level mixing as well as the possibility of new near-threshold resonances in $c\bar c, b\bar b$ systems. The Weinberg eigenvalue method is formulated in the multichannel problems, which allows to describe coupled-channel resonances and wave functions in a unitary way, and to predict new states due to channel coupling. Realistic wave functions for all single-channel states and decay matrix elements computed earlier are exploited, and no new fitting parameters are involved. Examples of level shifts, widths and mixings are presented; the dynamical origin of X(3872) and the destiny of the single-channel $2^3P_1(c\bar c)$ state are clarified. As a result a sharp and narrow peak in the state with quantum numbers $J^{ PC}=1^{ ++}$ is found at 3.872 GeV, while the single-channel resonance originally around 3.940 GeV, becomes increasingly broad and disappears with growing coupling to open channels.
Categories: hep-ph hep-ex