Identification of the G(3900) Structure as the P-Wave DD[over ¯]^{*}/D[over ¯]D^{*} Resonance.

The BESIII Collaboration recently performed a precise measurement of the e^{+}e^{-}→DD[over ¯] Born cross sections, and confirmed the G(3900) structure reported by BABAR and Belle with high significance. We identify the G(3900) as the first P-wave DD[over ¯]^{*}/D[over ¯]D^{*} molecular resonance. The experimental and theoretical identification of the P-wave dimeson state holds paramount importance in enhancing our comprehension of the nonperturbative QCD and few-body physics. Its existence is firmly established in a unified meson-exchange model that simultaneously depicts the features of the χ_{c1}(3872), Z_{c}(3900), and T_{cc}(3875). This scenario can be directly examined in the e^{+}e^{-}→DD[over ¯]^{*}/D[over ¯]D^{*} cross section by seeing whether a resonance exists at the threshold. The credibility of the investigations is also ensured by the fact that the P-wave interaction dominantly arises from the well-known long-range pion exchange. Additionally, thanks to the centrifugal barrier, it is easier to form resonances in P-wave than in S-wave. We extensively calculate all systems up to P-wave with various quantum numbers and predict a dense population of the DD[over ¯]^{*}/D[over ¯]D^{*} and DD^{*} states, where the S-wave DD[over ¯]^{*}/D[over ¯]D^{*} state with I^{G}(J^{PC})=0^{-}(1^{+-}), P-wave DD[over ¯]^{*}/D[over ¯]D^{*} state with I^{G}(J^{PC})=0^{+}(0^{-+}), and P-wave DD^{*} state with I(J^{P})=0(0^{-}) are more likely to be observed in experiments.