Transverse beam polarization and CP-violating triple gauge-boson couplings in e⁺e⁻→γZ

Abstract

We show that an anomalous CP-violating γγZ vertex gives rise to a novel asymmetry with transversely polarized electron and positron beams in the process e⁺e⁻→γZ. This asymmetry, which is odd under naive time reversal, is proportional to the real part of the γγZ CP-violating coupling. This is in contrast to the simple forward-backward asymmetry of the γ (or Z) with unpolarized or longitudinally polarized beams studied earlier, which is even under naive time reversal, and is proportional to the imaginary part. We estimate the sensitivity of future experiments to the determination of CP-odd γγZ and γZZ couplings using these asymmetries and transversely polarized beams.