Search for New Hadronic States $W_{bj}$ in Belle data

Recent discovery of $Z_b$ states at the Belle experiment implies possible existence of a new family of hadronic resonances including molecular states dubbed $W_{bj}$. We search for these states in radiative decays of $\Upsilon(5S)$ resonance in data collected with the Belle detector at the KEKB asymmetric-energy electron-positron collider. No such additional hadronic states in the $Z_b$ family have been observed yet. We use Monte Carlo simulation to study Belle sensitivity to $W_{bj}$ production. We report the current status of our investigations to provide the best sensitivity to this decay in the existing data and to create a roadmap for future discovery.