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

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• 作者：Stanley J. Brodsky^a ; Richard F. Lebed^b ; Valery E. Lyubovitskij^c ; ^d ; ^e ; ^{lubovit@tphys.physik.uni-tuebingen.de}
• 关键词：Electron&ndash ; positron annihilation ; Hadron structure ; Quantum chromodynamics ; Vector meson dominance ; Electroweak bosons ; Tetraquarks
• 刊名：Physics Letters B
• 出版年：2017
• 出版时间：10 January 2017
• 年：2017
• 卷：764
• 期：Complete
• 页码：174-179
• 全文大小：330 K
• 卷排序：764

文摘

We study the exclusive double-photon annihilation processes, e+e−→γγ⁎→γV0e+e−→γγ⁎→γV0 and e+e−→γ⁎γ⁎→Va0Vb0, where the Vi0 is a neutral vector meson produced in the forward kinematical region: s≫−ts≫−t and −t≫ΛQCD2. We show how the differential cross sections dσdt, 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-θCMθCM 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−→γ⁎→qq¯, these total cross sections σ(e+e−→γV0)σ(e+e−→γV0) and σ(e+e−→Va0Vb0), integrated over the dominant forward- and backward-θCMθCM angular domains, scale as 1/s1/s, and thus contribute to the leading-twist scaling behavior of the ratio Re+e−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−→Z0V0e+e−→Z0V0 and e+e−→W−ρ+e+e−→W−ρ+. 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.