The extraction of the B→K∗ transition form factors from lattice data is studied, applying non-relativistic effective field theory in a finite volume. The possible mixing of πK and ηK states is taken into account. The two-channel analogue of the Lellouch-L\"uscher formula is reproduced. Due to the resonance nature of the K∗, an equation is derived, which allows to determine the form factors at the pole position in a process-independent manner. The infinitely-narrow width approximation of the results is discussed.
@article{arxiv.1605.03386,
title = {The $B\to K^*$ form factors on the lattice},
author = {Andria Agadjanov and Véronique Bernard and Ulf-G. Meißner and Akaki Rusetsky},
journal= {arXiv preprint arXiv:1605.03386},
year = {2016}
}