Search for $B$ decays to final states with the $\eta_c$ meson

TL;DR

This paper reports a search for specific $B$ meson decays involving the $ a_c$ meson and potential molecular states, setting upper limits on their branching fractions using data from the Belle detector at KEKB.

Contribution

The study provides the first upper limits on branching fractions for these $B$ decay modes and searches for molecular-state candidates related to the $Z$ and $X$ states.

Findings

No significant signals observed for the studied decay modes.

Set upper limits on branching fractions ranging from 0.6 to 5.3 times 10^{-4}.

Set upper limits on intermediate state products from 0.6 to 6.9 times 10^{-5}.

Abstract

We report a search for $B$ decays to selected final states with the $\eta_c$ meson: $B^{\pm}\to K^{\pm}\eta_c\pi^+\pi^-$, $B^{\pm}\to K^{\pm}\eta_c\omega$, $B^{\pm}\to K^{\pm}\eta_c\eta$ and $B^{\pm}\to K^{\pm}\eta_c\pi^0$. The analysis is based on $772\times 10^6$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We set 90% confidence level upper limits on the branching fractions of the studied $B$ decay modes, independent of intermediate resonances, in the range $(0.6-5.3)\times 10^{-4}$. We also search for molecular-state candidates in the $D^0\bar{D}^{*0}-\bar{D}^0D^{*0}$, $D^0\bar{D}^0+\bar{D}^0D^0$ and $D^{*0}\bar{D}^{*0}+\bar{D}^{*0}D^{*0}$ combinations, neutral partners of the $Z(3900)^{\pm}$ and $Z(4020)^{\pm}$, and a poorly understood state $X(3915)$ as possible intermediate states in the decay chain, and set 90% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range $(0.6-6.9)\times 10^{-5}$.