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.
Highlights
A future linear e+e− collider operating at a centre-of-mass energy of several hundred GeV would contribute greatly to a precise determination of the parameters of known particles and their interactions, as well as to the constraining of new physics
In [7] it was pointed out that an azimuthal distribution of a final-state particle A in a semiinclusive process e+e− → A + X arising from the interference between a standard model (SM) contribution and a new-physics contribution arising at some high scale cannot contain a CP-violating part if the new-physics contribution arises from chirality-conserving vector (V) or axial-vector (A) type of interaction, neglecting the electron mass
In this paper we investigate the interesting possibility that if there is transverse polarization, a T-odd but CP-even azimuthal asymmetry can be combined with the T-even but CP-odd forward-backward asymmetry to give an asymmetry which is both CP odd as well as T odd
Summary
A future linear e+e− collider operating at a centre-of-mass (cm) energy of several hundred GeV would contribute greatly to a precise determination of the parameters of known particles and their interactions, as well as to the constraining of new physics. The above results were obtained with the condition that the SM contribution arises only through s-channel exchange of virtual photon and Z. It is well-known that such an asymmetry could arise without transverse polarization (see, for example, [12, 13, 14]).
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