Finite Volume Corrections to the Two-Particle Decay of States with Non-Zero Momentum

We study the effects of finite volume on the two-particle decay rate of an unstable state with non-zero momentum. First Luscher's field-theoretic relation between the infinite volume scattering phase shifts and the quantized energy levels of a finite volume, two-particle system is generalized to the case of non-zero total momentum and compared with the earlier results of Rummukainen and Gottlieb. We then use this result and the method of Lellouch and Luscher to determine the corrections needed for a finite-volume calculation of a two-particle decay amplitude when the decaying particle has non-vanishing center-of-mass momentum.