Disentangling the global multiplicity and spectral shape fluctuations in radial flow

Radial flow is a key collective phenomenon in heavy-ion collisions, manifests through event-by-event fluctuations in transverse momentum ($p_{\mathrm{T}}$) spectra. The $p_{\mathrm{T}}$-differential radial flow, $v_0(p_{\mathrm{T}})$, initially conceived to capture local spectral shape fluctuations, is influenced by global multiplicity fluctuations. Using the HIJING model, we explore how different definitions of event activity for centrality and spectral normalization schemes affect $v_0(p_{\mathrm{T}})$. We find these methodological variations induce a constant offset in $v_0(p_{\mathrm{T}})$ without altering its shape, indicating that the dynamic $p_{\mathrm{T}}$-differential information on radial flow remains robust, but its absolute magnitude is meaningful only up to a baseline offset dictated by global multiplicity fluctuations.