2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/178751Using the upgraded Beijing Spectrometer (BESII), we have measured the total cross section for $e^+e^-$ annihilation into hadronic final states at center-of-mass energies of 2.6, 3.2, 3.4, 3.55, 4.6 and 5.0 GeV. Values of $R$, $σ(e^+e^-\to {hadrons})/σ(e^+e^-\toμ^+μ^-)$, are determined.Submitted to Phys. Rev. LettHigh Energy Physics - Experimenttext