The “NanGaoShi·Physics Seminar” series lectures hosted by the School of Physics Science and Technology of Nanjing Normal University were successfully held on June 4, 2026, in Room 437, Xingjian Building. We were honored to invite Associate Professor Sen Jia from Southeast University to give an academic lecture entitled “First Indication of the X(3872)→pi0 chi_c0 Decay and Measurement of the Mass Splitting of Upsilon_J(1D) Particles at the Belle II Experiment” The lecture was chaired by Professor Kai Yi from the School of Physics Science and Technology, and was attended by faculty members and graduate students in particle physics–related fields.

During the report, Associate Professor Sen Jia systematically presented two recent physics results based on Belle and Belle II data. Using a combined data sample of 1.2 ab^-1 accumulated by the two experiments, the research team captured the first indication of the X(3872)→π⁰ χ_c0 decay process in B meson decays. As an exotic hadronic state, the internal structure of X(3872) has remained unresolved. The discovery of this new decay channel provides crucial experimental information for probing its internal composition and helps to further constrain theoretical models.

In the study of bottomonium spectroscopy, the team made full use of Belle and Belle II data above the BBbar threshold and systematically measured the e⁺e⁻→η Υ_J(1D) and e⁺e⁻→π⁺π⁻Υ_J(1D) processes, observing for the first time clear indications of the Υ₁(1D) and Υ₃(1D) states and precisely determining the mass splitting between different states. This mass splitting provides a key experimental basis for distinguishing among the various potential models.

After the presentation, faculty and students actively raised questions regarding the content discussed. Associate Professor Sen Jia provided detailed responses to each query, leaving the audience greatly inspired.

Sen Jia --- Profile

Sen Jia, Associate Professor and doctoral supervisor at the School of Physics, Southeast University. He received his Ph.D. from Beihang University in 2020, and was a joint Ph.D. student at the High Energy Accelerator Research Organization – KEK -- in Japan from 2017 to 2019. From 2020 to 2022, he served as a postdoctoral fellow at Fudan University. He joined Southeast University in October 2022. His research focuses on experimental hadron physics, and he is a member of the Belle II and BESIII experimental collaborations. He currently serves as the convener of the Quarkonium Physics Group of the Belle II experiment and the deputy leader of the Belle II China group. As the actual first author/corresponding author, he has published more than 20 papers in academic journals such as PRL, Sci.Bull., JHEP, PRD.