Reevaluating the ψ(4160) resonance parameter using B+→K+μ+μ− data in the context of unquenched charmonium spectroscopy

Abstract

A puzzling phenomenon, where the measured mass of the ψ(4160) is pushed higher, presents a challenge to current theoretical models of hadron spectroscopy. This study suggests that the issue arises from analyses based on the outdated quenched charmonium spectrum. In the past two decades, the discovery of new hadronic states has emphasized the importance of the unquenched effect. Under the unquenched picture, six vector charmonium states—ψ(4040), ψ(4160), ψ(4220), ψ(4380), ψ(4415), and ψ(4500)—are identified in the 4–4.5 GeV range, contrasting with the three states predicted in the quenched model. We reevaluate the resonance parameters of the ψ(4160) using the dimuon invariant mass spectrum of B+→K+μ+μ− and unquenched charmonium spectroscopy. Our analysis indicates previous experimental overestimations for the mass of the ψ(4160). This conclusion is supported by analyzing e+e−→DsD¯s*, which finds the ψ(4160) mass at 4145.76±4.48 MeV. Our findings have significant implications for both hadron spectroscopy and search for new physics signals by RK. Published by the American Physical Society 2025