Solution
= Solution
The result grows linearly with the squared <centre-of-momentum energy>, $\sigma\propto G_F^2s$. This growth eventually violates <partial-wave unitarity> and signals the breakdown of the pointlike <Fermi interaction>. At energies comparable to $M_W$ or $M_Z$, the full gauge-boson propagators must replace the contact interaction; the renormalizable electroweak theory then softens the high-energy behavior.