Measurement of the energy dependence of the e⁺e⁻ → BB̄, BB̄^*, and B^*B̄^* cross sections at Belle~II

We report measurements of the e⁺e⁻ → BB̄, BB̄^*, and B^*B̄^* cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle~II experiment. We reconstruct one B meson in a large number of hadronic final states and use its momentum to identify the production process. In the first $2-5$ MeV above B^*B̄^* threshold, the e⁺e⁻ → B^*B̄^* cross section increases rapidly. This may indicate the presence of a pole close to the threshold.