Tetraquark interpretation of $e^+ e^- \to \Upsilon \pi^+\pi^-$ Belle data and $e^+ e^- \to b \bar{b}$ BaBar data

Abstract

We summarize the main features of the spectroscopy, production and decays of the $J^{PC}=1^{--}$ tetraquarks in the $b\bar{b}$ sector, concentrating on the lowest state called $Y_b(10890)$. The tetraquark framework is used to analyze the BaBar data on the $e^+ e^- \to b\bar{b}$ cross section ($R_b$ energy scan) between $\sqrt{s}= 10.54$ and 11.20 GeV and the Belle data on the processes $e^+e^- \to \Upsilon(1S) \pi^+\pi^-,\Upsilon(2S) \pi^+\pi^-$ near the peak of the $\Upsilon(5S)$ resonance. The BaBar $R_b$ energy scan is consistent with an additional state at a mass of 10.90 GeV and a width of about 28 MeV, in broad agreement with the state $Y_b(10890)$ GeV seen by Belle in the exclusive final states. We argue that the decay widths and the dipion invariant mass distributions measured by Belle are naturally explained by the tetraquark interpretation of $Y_b(10890)$.