Observation of the $B^0_s\to\eta'\eta'$ decay

TL;DR

This paper reports the first observation of the rare decay $B^0_s o ext{ exteta'} ext{ exteta'}$, measuring its branching fraction and charge asymmetries, confirming theoretical predictions with high statistical significance.

Contribution

The study provides the first experimental observation and measurement of the $B^0_s o ext{ exteta'} ext{ exteta'}$ decay, expanding knowledge of rare B meson decays.

Findings

Signal significance of 6.4 standard deviations.

Branching fraction measured as approximately 3.31 x 10^{-5}.

Charge asymmetries consistent with theoretical expectations.

Abstract

The first observation of the $B^0_s\to\eta'\eta'$ decay is reported. The study is based on a sample of proton-proton collisions corresponding to $3.0$ ${\rm fb^{-1}}$ of integrated luminosity collected with the LHCb detector. The significance of the signal is $6.4$ standard deviations. The branching fraction is measured to be $[3.31 \pm 0.64\,{\rm (stat)} \pm 0.28\,{\rm (syst)} \pm 0.12\,{\rm (norm)}]\times10^{-5}$, where the third uncertainty comes from the $B^{\pm}\to\eta' K^{\pm}$ branching fraction that is used as a normalisation. In addition, the charge asymmetries of $B^{\pm}\to\eta' K^{\pm}$ and $B^{\pm}\to\phi K^{\pm}$, which are control channels, are measured to be $(-0.2 \pm1.3)\%$ and $(+1.7\pm1.3)\%$, respectively. All results are consistent with theoretical expectations.