QCD compositeness as revealed in exclusive vector boson reactions through double-photon annihilation: e+e- → γγ* → γV0 and e+e- → γ*γ* → V0V0

We study the exclusive double-photon annihilation processes, e(+)e(-) -> gamma gamma* -> gamma V-0 and e(+)e(-) -> gamma*gamma* -> (VaVb0)-V-0, where the V-i(0) is a neutral vector meson produced in the forward kinematical region: s >> -t and -t >>Lambda(2)(QCD). We show how the differential cross sections d theta/dt, as predicted by QCD, have additional falloff in the momentum transfer squared t due to the QCD compositeness of the hadrons, consistent with the leading-twist fixed-theta(CM) scaling laws, both in terms of conventional Feynman diagrams and by using the AdS/QCD holographic model to obtain the results more transparently. However, even though they are exclusive channels and not associated with the conventional electron-positron annihilation process e(+)e(-) -> gamma* -> q (q) over bar, these total cross sections sigma(e(+) e(-) -> gamma V-0) and sigma(e(+)e(-) -> V-a(0) V-b(0)), integrated over the dominant forward-and backward-theta(CM) angular domains, scale as 1/s, and thus contribute to the leading-twist scaling behavior of the ratio Re+ e-. We generalize these results to exclusive double-electroweak vector-boson annihilation processes accompanied by the forward production of hadrons, such as e(+) e(-) -> Z(0)V(0) and e(+) e(-) -> W- rho(+). These results can also be applied to the exclusive production of exotic hadrons such as tetraquarks, where the cross-section scaling behavior can reveal their multiquark nature. (C) 2016 The Author(s). Published by Elsevier B.V.