Precise measurement of the χ_c0 resonance parameters and branching fractions of χ_c0,_c2 → π⁺π⁻/K⁺K⁻

By analyzing a ψ(3686) data sample containing (107.7±0.6)×10⁶ events taken with the BESIII detect- or at the BEPCII storage ring in 2009, the χ_c0 resonance parameters are precisely measured using χ_c0,c2 → π⁺π⁻/K⁺K⁻ events. The mass of χ_c0 is determined to be M(χ_c0) = (3415.63±0.07±0.07±0.07) MeV/c², and its full width is Γ(χ_c0) = (12.52±0.12±0.13) MeV, where the first uncertainty is statistical, the second systematic, and the third for mass comes from χ_c2 mass uncertainty. These measurements improve the precision of χ_c0 mass by a factor of four and width by one order of magnitude over the previous individual measurements, and significantly boost our knowledge about the charmonium spectrum. Together with additional (345.4±2.6)×10⁶ ψ(3686) data events taken in 2012, the decay branching fractions of χ_c0,c2 → π⁺π⁻/K⁺K⁻ are measured as well, with precision improved by a factor of three compared to previous measurements. These χ_c0 decay branching fractions provide important inputs for the study of glueballs.