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摘要：
I explain our recent studies on generalized parton distributions (GPDs) and spin-1 structure functions.
The t-channel or spacelike (s-channel or timelike) GPDs are studied by deeply virtual Compton scattering (two-photon processes) at charged-lepton accelerator facilities (e^+e^- collider facilities) such as the JLab and EICs (KEKB, BES). Here, the s-channel GPDs are generally called generalized distribution amplitudes (GDAs) and they could be also called timelike GPDs because they contain timelike form factors. I discuss projects mainly at the e^+e^- collider KEKB (or BES) [1], the hadron-accelerator facility J-PARC (or HIAF) [2], and the Long-Baseline Neutrino Facility (LBNF) at Fermilab [3]. It is possible to extract gravitational form factors of hadrons from these measurements [1].
Structure functions of the spin-1 deuteron will be investigated experimentally from the late 2020's at various facilities such as JLab, Fermilab, NICA, and EICs. We expect that a new high-energy spin-physics field could be created by these projects. In Ref. [4], the current theoretical status is explained for the structure functions of spin-1 hadrons, especially on parton distribution functions, transverse-momentum dependent parton distributions, and fragmentation functions. I also comment on the GPDs of the spin-3/2 Delta [5].
References
[1] S. Kumano, Qin-Tao Song, and O. V. Teryaev, Phys. Rev. D 97, 014020 (2018).
[2] S. Kumano, M. Strikman, and K. Sudoh, Phys. Rev. D 80, 074003 (2009), T. Sawada et al., Phys. Rev. D 93, 114034 (2016).
[3] X. Chen, S. Kumano, R. Kunitomo, S. Wu, and Y.-P. Xie, Euro. Phys. J. A60 (2024) 208.
[4] S. Kumano, Euro. Phys. J. A 60 (2024) 205. See also W. Cosyn, Y.-B. Dong, S. Kumano, M. Sargsian, Phys. Rev. D 95 (2017) 074036.
[5] D.-Y. Fu, Y.-B. Dong, S. Kumano, Phys. Rev. D 109 (2024) 096006; arXiv:2508.15245.
个人简介：Shunzo Kumano is emeritus professors of KEK and Graduate University for Advanced Studies, and he is also a diamond fellow of KEK. He was the head of hadron theory group in the Theory center, Institute of particle and nuclear studies at KEK, Japan. He has been investigating parton distribution functions, fragmentation functions, and high-energy hadron reactions for clarifying the structure of the nucleon and nuclei. His recent interests include the origin of nucleon spin, nucleon tomography, and exotic hadrons. Now, he is a professor at Institute of Modern Physics and Southern Center for Nuclear-Science Theory, Huizhou, China.