Baryon-number violation with improved instantons

We consider the question of possible baryon-number violation at TeV energies in electroweak theory. We prove that already at much lower energies, the usual O(4)-symmetric instantons are the wrong ones to use. The true instantons, which we exhibit, are only O(3) symmetric, and in the example we work out reduce the initial rise in the baryon-number-violating cross section by a factor of 4 in the exponent, in accord with a diagrammatic analysis. Our approach appears extendable to energies of the order of the sphaleron mass.