$γ$ - Z interferometry at a $Φ$-factory

Abstract

We analyze the possibilities that the proposed $Φ$-factories offer to measure $γ-Z$ interference. In the unpolarized beam case, we study different signatures in the $ρπ$ channel, taking advantage of the presence of the near-by $a_1$ resonance. We build a C-odd forward-backward asymmetry, estimated to be around $10^{-5}$, and (P-even, T-even) and (P-odd, T-odd) alignments of the $ρ$, to be seen from the angular distribution of its $ππ$ decay products. With polarized electrons a left-right asymmetry around $2\times 10^{-4}$ is present in all channels. At leading order this asymmetry is independent of hadronic matrix elements and is sensitive to the $Z^0-s\bar{s}$ vector coupling. In the $ρπ$ channel, a combined left-right forward-backward asymmetry is considered.