Search for the Decay \(B \rightarrow {D^{*}} \eta \pi \) in Belle II

Recent measurements of semileptonic decays show a difference between the branching ratio of the sum of exclusive decay rates and the inclusive \(b \rightarrow c \ell \nu \) decay rate (the so-called Semi-Leptonic (SL) gap) which affects the interpretation of the CKM element |Vcb|. Large contributions from not-yet measured \(B \rightarrow D^* \eta \ell \nu \) decays could explain such difference. We present a study of the \(B \rightarrow D^* \eta \pi \) decay on the simulated data sample of the Belle II experiment. This measurement will provide valuable information to predict its semileptonic counterpart \(B \rightarrow D^* \eta \ell \nu \) . If \(B \rightarrow D^* \eta \pi \) decay is found to be large, it could contribute significantly to the hadronic B-tagging, and consequently enhance the sensitivity for searching rare B decays with missing energy.