Spin and chirality effects in antler-topology processes at high energy e^+e^- colliders

We perform a model-independent investigation of spin and chirality correlation effects in the antler-topology processes e^+e^-→𝒫^+𝒫^-→ (ℓ ^+ 𝒟^0) (ℓ ^-𝒟̅^0) at high-energy e^+e^- colliders with polarized beams. Generally the production process e^+e^-→𝒫^+𝒫^- can occur not only through the s -channel exchange of vector bosons, 𝒱^0 , including the neutral Standard Model (SM) gauge bosons, γ and Z , but also through the s - and t -channel exchanges of new neutral states, 𝒮^0 and 𝒯^0 , and the u -channel exchange of new doubly charged states, 𝒰^– . The general set of (non-chiral) three-point couplings of the new particles and leptons allowed in a renormalizable quantum field theory is considered. The general spin and chirality analysis is based on the threshold behavior of the excitation curves for 𝒫^+𝒫^- pair production in e^+e^- collisions with longitudinal- and transverse-polarized beams, the angular distributions in the production process and also the production-decay angular correlations. In the first step, we present the observables in the helicity formalism. Subsequently, we show how a set of observables can be designed for determining the spins and chiral structures of the new particles without any model assumptions. Finally, taking into account a typical set of approximately chiral invariant scenarios, we demonstrate how the spin and chirality effects can be probed experimentally at a high-energy e^+e^- collider.