Mode-Aware Recoil Anti-Kick Morphology in Nonspinning Binary Black Hole Mergers

This record contains a short numerical-relativity research note and supporting materials for a study of recoil anti-kick morphology in nonspinning unequal-mass SXS binary black hole simulations. The central observable is the fractional recoil anti-kick amplitude [Rₐₙₜᵢ=(vₚₑₐₖ-vfinal)/vfinal,] where (vₚₑₐₖ) is the maximum magnitude of the waveform-integrated recoil history and (vfinal) is the final recoil speed. Recoil histories are reconstructed from strain-derived News fields and validated by closure against SXS catalog remnant velocities. The main empirical result is that (Rₐₙₜᵢ) decreases monotonically with mass ratio in both (≤3) and (≤4) angular-mode truncations. Including (=4) modes raises the absolute normalization of (Rₐₙₜᵢ) by approximately 0.12–0.13 across the tested range, but does not alter the monotonic trend. The mass-asymmetry parameter (δ=(q-1)/(q+1)) provides the cleanest one-parameter empirical description. This upload is intended as a timestamped open-access preprint record while arXiv gr-qc submission/endorsement is pursued.