Unknown size of higher-order HQE terms
Ascertain the size of the currently uncalculated higher-order terms in the heavy-quark expansion for inclusive semileptonic B→X_cℓν decays to enable disentangling potential quark–hadron duality–violating contributions from genuine higher-order HQE effects in global analyses.
References
However, since we do not know the size of the higher-order terms of the HQE series, it may be hard to disentangle a small duality-violating effects from the unknown higher orders in $1/m_b$.
— Quark-Hadron Duality Violations and Higher-Order $1/m_b$ Corrections in Inclusive Semileptonic $B$ Decays
(2407.01473 - Mannel et al., 1 Jul 2024) in Section 6 (Quantifying Duality Violations from Data)