We present a first N f = 2 lattice estimate of the hadronic coupling g12 which parametrises the strong decay of a radially excited B * meson into the ground state B meson at zero recoil. We work in the static limit of Heavy Quark Effective Theory (HQET) and solve a Generalised Eigenvalue Problem (GEVP), which is necessary for the extraction of excited state properties. After an extrapolation to the continuum limit and a check of the pion mass dependence, we obtain g12 = −0.17(4).

This letter reports on the first computation, from data obtained in lattice QCD with u, d, s and c quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the MOM Taylor scheme. We provide with estimates of α MS (m 2 τ ) and α MS (m 2 Z ) in very good agreement with experimental results. Including a dynamical c quark makes safer the needed running of α MS .