On December 12, the reporter learned from the Institute of Modern Physics of the Chinese Academy of Sciences that its researchers and collaborators carried out high-precision measurement of the decay properties of proton drip line nuclear phosphorus 26 relying on the large scientific device of the Lanzhou heavy ion accelerator, and found that β The strongest isospin hybrid phenomenon in decay directly challenges people's understanding of nuclear interaction. The research results were published in the Physical Review Letters recently. Symmetry is a core concept in modern physics, which widely exists in nature. Symmetry breaking often implies new physics. In 1932, Heisenberg put forward the concept of isospin, which regarded protons and neutrons as two states of the same particle. In the case of isospin strict symmetry, β In the decay, the Fermi transition is only distributed to isospin like states. However, the break of isospin symmetry will lead to the splitting of Fermi transition intensity, which will not only inhabit the isospin similar state, but also the excited state near the isospin similar state. Previously, only a few cases of this isospin mixing phenomenon were found in the experiment, and the isospin mixing matrix elements were all less than 50keV, which can basically explain these phenomena in theory. The researchers of the Nuclear Physics Center of the Institute of Modern Physics carried out the research of the strange atomic nucleus P-26 based on the Lanzhou Heavy Ion Accelerator Radioactive Beam Line (HIRFL-RIBLL1) β The correlation measurement of delayed biproton emission found for the first time two highly excited states 11912 keV and 13380 keV near the isospin similar state of silicon-26. Based on the high-precision experimental data, the researchers obtained that the isospin hybrid matrix element of the silicon 26 isospin similar state 13055keV and the highly excited state 13380keV is 130keV, which is found in the current experiment β The physical cause behind the strongest isospin hybrid phenomenon in decay may be weak binding or large deformation effect. However, the isospin hybrid matrix elements calculated by various theoretical models for P-26 decay are all less than 30 keV, far less than the experimental value. The experimental results pose a strong challenge to existing theoretical research and will promote the development of nuclear interaction theory. This research was led by the Institute of Modern Physics of the Chinese Academy of Sciences and completed by 23 domestic and foreign scientific research institutions, including Sun Yat sen University and Shanghai Jiao Tong University. (Reporter Jie Manbin) (Liaoxin News Agency)