Gamow-Teller matrix elements from the B11(p,n)11C reaction at Ep26 MeV

New data are presented for the B11(p,n)11C reaction taken at 1 MeV intervals for proton bombarding energies in the Ep=16-26 MeV range. In the experiment, final states in C11 up to Ex10 MeV were clearly identified and differential cross sections were extracted for the first four levels in C11. The Ep=26 MeV data are examined in microscopic distorted-wave approximation calculations using the wave functions of Cohen and Kurath to describe the states in B11 and C11 and using the G matrix interaction of Bertsch et al. for the effective nucleon-nucleon interaction. Gamow-Teller matrix elements for transitions to excited states in C11 are extracted on the basis of these calculations, thus extending the information on Gamow-Teller matrix elements in the mass 11 systems beyond the ground state matrix element known from β decay. Throughout, the results are contrasted with existing information from electromagnetic studies of B11. It is concluded that the Cohen-Kurath model places too much Gamow-Teller strength in the low lying states of the mass 11 systems and not enough strength at higher excitation energies. In addition, this model underestimates the net contribution to M1 matrix elements from the isoscalar spin and current and isovector current parts of the M1 operator.