A method of looking for bottomonia transitions has been developed
at the Belle collaboration.
This method allowed to find and study transitions between
Υ(4S) and Υ(1S) states with the emission of charged
pions using of data collected with the Belle detector at
the KEKB asymmetric-energy e+ e− collider.
The branching fraction and partial width of this transition
has been measured.
The dynamics of this decay was studied.
The Υ(5S) decay to Υ(nS) and
π(K)+ π(K)− has been
observed at the Belle experiment for the first time.
The measured partial width exceeds by more than two orders of
magnitude the partial widths for dipion transitions
between lower Upsilon resonances.
The reasons for this phenomenon are discussed.