Abstract: Recent experimental anomalies in subatomic particle lifetimes—specifically the decay ratios between muon and tau leptons—remain unresolved by the Standard Model’s gauge boson exchange framework. This study demonstrates that subatomic particles behave as stable toroidal vortices (topological solitons) within a superfluid vacuum characterized by a constant dynamic viscosity \eta \approx 24.04 \text{ s}^{-1}. We show that the decay of these vortices is not a probabilistic event, but a deterministic hydrodynamic process governed by viscous dissipation. By modeling the decay rate as a function of the vortex's mass-energy dissipation against the vacuum's intrinsic viscosity, we derive a universal power law where the decay rate \Gamma scales as M^5. This result aligns with the observed 1.35 million-fold difference in lifetime between the muon and tau lepton. Our derivation replaces ad-hoc weak-force constants with an integrated hydrodynamic stress-energy tensor, providing a parameter-free explanation for subatomic stability and decay.