Example of the invariant-mass (\Minv) spectrum for a specific transverse momentum interval of the $\uprho^{0}$ meson, obtained by combining $\uppi^{+}\uppi^{-}$ pairs using their rest mass, as reported in the PDG . The spectrum, parameterized with a Breit--Wigner function, is used for the purity estimation of the $\uprho^{0}$ candidates (green). The K$^{0}_{\mathrm{S}}$ contribution (orange) is modeled with a Gaussian function. The $\omega$(782) contribution (violet) is extracted from simulation. The residual background (blue) is parameterized with an exponential function. The $\uprho^{0}$ candidates are selected within the mass window $0.70$--$0.85$ \GeVmass (indicated by long-dashed lines). The dotted lines indicate the signal and sideband regions, respectively.