Belle II Constraints on the Non-Minimal Universal Extra Dimensional Model

Recent measurements by the Belle II Collaboration report a branching ratio for the decay $B^+\to K^+ ν\barν$ with a 3.5$σ$ significance and deviating by 2.7$σ$ from Standard Model expectation. In this article, we interpret this experimental result through the lens of a Non-minimal Universal Extra Dimensional model, where the mass profiles and interactions among various Kaluza-Klein states differ remarkably from those in the minimal scenario. Our analysis indicates that, according to the model's parameters, the lower limit on the inverse of the compactification radius has been elevated to approximately 900 GeV. Conversely, the same analysis in the minimal version of the model does not allow for the establishment of a lower limit on the inverse of the compactification radius.