Hindered M1 radiative decay of Υ(2S) from lattice NRQCD

We present a calculation of the hindered M1 Upsilon(2S) -> eta(b)(1S)gamma decay rate using lattice nonrelativistic quantum chromodynamics. The calculation includes spin-dependent relativistic corrections to the NRQCD action through O(v(6)) in the quark's relative velocity, relativistic corrections to the leading order current which mediates the transition through the quark's magnetic moment, radiative corrections to the leading spin-magnetic coupling and for the first time a full error budget. We also use gluon field ensembles at multiple lattice spacing values, all of which include u, d, s and c quark vacuum polarization. Our result for the branching fraction is B(Upsilon(2S) -> eta(b)(1S)gamma) = 5.4(1.8) x 10(-4), which agrees with the current experimental value.