Bottomonium dipion transitions

Abstract

Dipion transitions of the subthreshold bottomonium levels ${\rm Y}(nS)\to {\rm Y}(n^{\prime }S)\pi \pi$ with $n>n^{\prime },n=2,3,4,n^{\prime }=1,2$ are studied in the framework of the chiral decay Lagrangian, derived earlier. The channels $B\bar{B},B{\bar{B}}^{\ast }+c.c,B^{\ast }{\bar{B}}^{\ast }$ are considered in the intermediate state and realistic wave functions of ${\rm Y}(nS),B$ and $B^{\ast }$ 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.

Comments: 34 pages, 18 figures