$Z_b(10610)$ and $Z_b(10650)$ structures produced by the initial single pion emission in the $\Upsilon(5S)$ decays

TL;DR

This paper introduces the Initial Single Pion Emission mechanism in $$ decays, explaining the origin of the $Z_b(10610)$ and $Z_b(10650)$ structures observed by Belle through theoretical line shape analysis.

Contribution

It proposes a novel decay mechanism that accounts for the observed $Z_b$ structures in $$ decays, providing a natural explanation for these exotic states.

Findings

Sharp structures around 10610 MeV and 10650 MeV in line shapes

Theoretical line shapes match observed $Z_b$ structures

Supports the interpretation of $Z_b$ states as effects of initial single pion emission

Abstract

We propose an unique mechanism called {\it Initial Single Pion Emission} existing in the $\Upsilon(5S)$ decays, and further study the line shapes of $d\Gamma(\Upsilon(5S\to \Upsilon(nS)\pi^+\pi^-))/dm_{\Upsilon(nS)\pi^+}$ ($n=1,2,3$) and $d\Gamma(\Upsilon(5S\to h_b(mP)\pi^+\pi^-))/dm_{h_b(mP)\pi^+}$ ($m=1,2$). We find sharp structures around 10610 MeV and 10650 MeV in the obtained theoretical line shapes of $d\Gamma(\Upsilon(5S\to \Upsilon(nS)\pi^+\pi^-))/dm_{\Upsilon(nS)\pi^+}$ and $d\Gamma(\Upsilon(5S\to h_b(mP)\pi^+\pi^-))/dm_{h_b(mP)\pi^+}$ distributions, which could naturally correspond to the $Z_b(10610)$ and $Z_b(10650)$ structures newly observed by Belle.