Explain the detector-specific discrepancy in spin orientation inference for GW231123

Identify and account for the cause of the discrepancy between LIGO Hanford-only and LIGO Livingston-only analyses in the inferred spin orientations for GW231123, determining whether it arises from data characteristics, instrumental effects, or waveform-model limitations by reproducing or eliminating the effect with controlled injections and diagnostics.

Background

The authors report that Hanford-only analyses favor aligned spins, while Livingston-only analyses prefer misalignment, and the stronger Livingston signal dominates the network result.

Despite hypothesized explanations (e.g., lower signal power at Hanford), the discrepancy could not be reproduced with zero-noise injections, pointing to an unresolved issue needing targeted investigation.