Measurement of the energy dependence of the e^+e^- BB, BB^*, and B^*B^* cross sections at Belle~II

We report measurements of the e^+e^- BB, BB^*, and B^*B^* 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^*B^* threshold, the e^+e^- B^*B^* cross section increases rapidly. This may indicate the presence of a pole close to the threshold.