The spin alignment of vector mesons, characterized by the spin-density-matrix element ρ00, is an important observable for studying spin dynamics in relativistic heavy-ion collisions. Experimental measurements have reported deviations of ρ00 from the isotropic expectation of 1/3, motivating careful evaluation of possible acceptance effects. In this work, we investigate the influence of finite experimental coverage on the extracted ρ00 of K∗0 mesons using a toy model constrained by realistic kinematic distributions from the AMPT model. The reconstructed ρ00 is examined as a function of pseudorapidity (η) and transverse momentum (pT) within typical experimental acceptance ranges. We find that limited pseudorapidity coverage can lead to reconstructed ρ00 values above 1/3, even when the input distribution is isotropic. This behavior originates from the selective removal of decay daughters outside the η window, which modifies the cosθ∗ distribution. A dependence on transverse momentum is also observed, particularly at low pT where daughter particles are more sensitive to longitudinal acceptance constraints. Comparisons with STAR measurements are presented for reference, without attempting to reinterpret the experimental results. Overall, this study provides a systematic examination of acceptance-induced effects and may serve as a useful reference for future measurements of vector-meson spin alignment.
Lan et al. (Sat,) studied this question.