Addendum to “Scattering of twisted particles: Extension to wave packets and orbital helicity”

In a recent work [Phys. Rev. A 84, 033804 (2011)] we considered elastic scattering of a twisted particle from a plane wave and studied how the orbital helicity of the twisted particle changes after scattering. We showed that for realistic beams the relative change can be small, $|m^{\prime }-m|/m\ll 1$, thus resolving a controversy which existed in the literature. In this Addendum, using a more accurate analysis, we argue that in the kinematics of Compton backscattering a stronger statement is true: in fact $m^{\prime }\approx m$, and the difference $|m^{\prime }-m|$ even by a single unit is already suppressed.