1212.4066 (Xiao-Hai Liu et al.)

Extracting $ππ$ $S$-wave scattering lengths from cusp effect in
heavy quarkonium dipion transitions    [PDF]

Xiao-Hai Liu, Feng-Kun Guo, Evgeny Epelbaum

Charge-exchange rescattering $\pi^+\pi^-\to \pi^0\pi^0$ leads to a cusp effect in the $\pi^0\pi^0$ invariant mass spectrum of processes with $\pi^0\pi^0$ in the final state which can be used to measure $\pi\pi$ $S$-wave scattering lengths. Employing a non-relativistic effective field theory, we discuss the possibility of extracting the scattering lengths in heavy quarkonium $\pi^0\pi^0$ transitions. The transition $\Upsilon(3S)\to\Upsilon(2S)\pi^0\pi^0$ is studied in details. We discuss the precision that can be reached in such an extraction for a certain number of events.

View original: http://arxiv.org/abs/1212.4066