Totald+d→α+η cross sections near threshold

The total cross section for η production in deuteron-deuteron interactions has been measured at four different kinetic energies, from 0.7 MeV to 3.7 MeV above threshold. The squared amplitude is consistent with a constant value of ‖f${\mathrm{\Vert }}^2$=(24.6±1.2±1.7) nb/sr close to threshold (14<${\mathit{p}}_{\mathrm{\eta }}$<40 MeV/c). Assuming that the ${\mathrm{\pi }}^0$-η mixing reaction mechanism is dominant, this result allows a prediction of (dσ/dΩ${)}_{{\mathrm{\pi }}^0}$=(8.3±0.5 ±0.6) pb/sr for the cross section of the isospin-forbidden reaction d+d→α+${\mathrm{\pi }}^0$ at the η-threshold energy.