  XEFT is a low-energy effective field theory for charm mesons and pions that
provides a systematically improvable description of the $X(3872)$ resonance. To
simplify calculations beyond leading order, we introduce a new formulation of
XEFT with a dynamical field for a pair of charm mesons in the resonant channel.
We simplify the renormalization of XEFT by introducing a new renormalization
scheme that involves the subtraction of amplitudes at the complex $D^{*0} \bar
D^0$ threshold. The new formulation and the new renormalization scheme are
illustrated by calculating the complex pole energy of $X$ and the $D^{*0} \bar
D^0$ scattering amplitude to next-to-leading order using Galilean-invariant
XEFT.
