Search for an Axion-Like Particle in $B\to K^{(\ast )}a(\to {\hat{I}}^3{\hat{I}}^3)$ Decays at Belle

Abstract

We report a search for an axion-like particle $a$ in $B\to K^{(\ast )}a(\to {\hat{I}}^3{\hat{I}}^3)$ decays using data collected with the Belle detector at the KEKB asymmetric energy electron-positron collider. The search is based on a $711\mathrm{f}{\mathrm{b}}^{-1}$ data sample collected at the $\hat{I}\yen 4S$ resonance energy, corresponding to a sample of $772\times 10^6$ $\hat{I}\yen 4S$ events. In this study, we search for the decay of the axion-like particle into a pair of photons, $a\to {\hat{I}}^3{\hat{I}}^3$. We scan the two-photon invariant mass in the range $0.16GeV/c^2-4.50\mathrm{GeV}/c^2$ for the $K$ modes and $0.16GeV/c^2-4.20\mathrm{GeV}/c^2$ for the $K^{\ast }$ modes. No significant signal is observed in any of the modes, and 90\% confidence level upper limits are established on the coupling to the $W$ boson, $g_{a}W$, as a function of $a$ mass. The limits range from $3\times 10^{-6}{\mathrm{GeV}}^{-1}$ to $3\times 10^{-5}{\mathrm{GeV}}^{-1}$, improving the current constraints on $g_{a}W$ by a factor of two over the most stringent previous experimental results.

26 pages, 15 Figures