QCD sum-rule determination of the axial-vector mixing angle in the \texorpdfstring{\(B_c(1P)\)}{Bc(1P)} sector

Abstract

We determine the mixing angle between the \(1^1P_1\) and \(1^3P_1\) axial-vector states in the \(B_c(1P)\) sector using QCD sum rules. The analysis gives \(θ_{B_c(1P)}=(43.3\pm0.2)^\circ\), indicating sizable mixing between these two states. We also compare our result with theoretical studies available in the literature.