Amplitude analysis of e+e-→ (nS)π+π-at s =10.866GeV

We report results on studies of the e+e-annihilation into three-body (nS)π+π-(n=1,2,3) final states including measurements of cross sections and the full amplitude analysis. The cross sections measured at s=10.866GeV and corrected for the initial state radiation are σ(e+e-→ (1S)π+π-)=(2.27±0.12±0.14)pb, σ(e+e-→ (2S)π+π-)=(4.07±0.16±0.45)pb, and σ(e+e-→ (3S)π+π-)=(1.46±0.09±0.16)pb. Amplitude analysis of the three-body (nS)π+π-final states strongly favors IG(JP)=1+(1+) quantum-number assignments for the two bottomonium-like Zb± states, recently observed in the (nS)π± and hb(mP)π± (m=1,2) decay channels. The results are obtained with a 121.4fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e-collider.