η w -meson from topological properties of the electroweak vacuum

We further scrutinize the evidence for a recently suggested pseudoscalar particle, the electroweak η w meson. Its existence is demanded by matching the removal of the weak vacuum angle θ w by the anomalous B + L symmetry with a massive pole in the topological susceptibility of the vacuum. We specifically focus on the possibility of the emergence of η w as a collective excitation of the phase of the condensate of the ’t Hooft fermion determinant, generated by the electroweak instantons, which breaks the B + L symmetry spontaneously. We argue that the generation of the ’t Hooft vertex is in one-to-one correspondence with its nonzero vacuum expectation value which is cutoff insensitive. We outline certain puzzles about the nature of the emergent η w which require further investigation.