Bottomonium dipion transitions

Dipion transitions of the subthreshold bottomonium levels Y(nS) -> Y(n(l)S)pi pi with n > n(l), n = 2, 3, 4n(l) = 1,2 are studied in the framework of the chiral decay Lagrangian, derived earlier. The channels B (B) over bar, B (B) over bar* + c.c., B*(B) over bar* are considered in the intermediate state and realistic wave functions of Y(nS), B and B* are used in the overlap matrix elements. Imposing the Adler zero requirement on the transition matrix element, one obtains 2d and 1d dipion spectra in reasonable agreement with experiment.