Elastic double diffractive production of axial-vector χ_c (1^{+ +}) mesons and the Landau-Yang theorem

Summary, in English

We discuss exclusive elastic double diffractive axial-vector χ_c (1⁺) meson production in proton-antiproton collisions at the Tevatron. The amplitude for the process is derived within the k_t-factorization approach with unintegrated gluon distribution functions (UGDFs). We show that the famous Landau-Yang theorem is not applicable in the case of off-shell gluons. Differential cross sections for different UGDFs are calculated. We compare exclusive production of χ_c (1⁺) and χ_c (0⁺). The contribution of χ_c (1⁺) to the J / Ψ + γ channel is smaller than that of the χ_c (0⁺) decay, but not negligible and can be measured. The numerical value of the ratio of the both contributions is much less dependent on the UGDFs modeling than the cross sections themselves.