The “NanGaoShi·Physics Lecture” series lecture hosted by the School of Physics Science and Technology of Nanjing Normal University was successfully held on June 9, 2026, in Room 437, Xingjian Building. Professor Zheng Yangheng from University of Chinese Academy of Sciences delivered an insightful lecture titled “Direct observation of the Migdal effect induced by neutron bombardment”.

In January 2026, the MARVEL Collaboration announced the world’s first direct observation of the Migdal Effect, with relevant findings published in Nature. This breakthrough solved a long-standing physical puzzle first proposed back in 1939.

During the lecture, Professor Zheng first introduced the Migdal Effect and reviewed previous studies that only achieved indirect observation of the phenomenon. He elaborated on the experimental detector design and data analysis procedures in detail. To capture extremely faint nuclear recoil and electron signals, the research team independently developed an sensitive detection system centered on the GMCP detector and Topmetal chips. The team overcame technical challenges including charge accumulation and noise interference. The detector delivers excellent performance in energy resolution, vertex resolution and time resolution, enabling accurate discrimination between nuclear recoil signals and electron signals. The experiment was carried out using a deuterium-deuterium fusion neutron source. After around 150 hours of data collection and comprehensive background signal analysis to eliminate various interferences, researchers screened a total of 817,000 candidate events and finally identified 6 valid events featuring typical characteristics of the Migdal Effect. The result was verified with a statistical significance exceeding 5σ, and the transition probability was measured, which is consistent with theoretical predictions.

Professor Zheng also noted that the team has launched the upgrade of detection equipment. The effective area of the new detector has been increased by 10 times. In the next phase, the team will conduct precise measurements of the Migdal Effect cross sections for multiple elements, and adopt a 3D imaging TPC detector for the second-stage experiments.

About the speaker:

Professor Zheng Yangheng is the Vice President of the University of Chinese Academy of Sciences. He earned his bachelor’s degree from the University of Science and Technology of China in 1995, and his doctoral degree in experimental particle physics from the University of Hawaii, USA, in 2002. In 2007, he returned to China and established a particle physics experimental research team at the University of Chinese Academy of Sciences. He has held key positions including Physics Coordinator, Executive Committee Member and Co-Spokesperson for the BESIII Experiment. He has participated in multiple major international experiments, such as the Belle experiment at KEK, the CDF experiment at Fermilab, the CMS and LHCb experiments at the Large Hadron Collider.

Professor Zheng has made remarkable achievements in particle and radiation detector development, fundamental software research, hadron physics and flavor physics. His major accomplishments include discovering a series of exotic tetraquark hadrons, systematically studying the production and decay properties of Lambda_c charmed baryons, and realizing the first direct observation of the Migdal Effect predicted by quantum mechanics in 1939. He is now promoting the construction of the next-generation high-luminosity electron-positron collider.