J. Xu, Qinglin Niu, Yuhao Qin, Dawei Si, Yijie Wang, Sheng Xiao, Baiting Tian, Z. Qin, Haojie Zhang, Boyuan Zhang, Dong Guo, MinXue Fu, Xiaobao Wei, Yibo Hao, Zengxiang Wang, Tianren Zhuo, Chun-Wang Ma, Yuansheng Yang, Xianglun Wei, Herun Yang, Peng Ma, Limin Duan, Fangfang Duan, K. Wang, Junbing Ma, Shiwei Xu, Zhen Bai, Yang Guo, Y. Y. Yang, M. Xu, Kai-Jie Chen, Zirui Hao, Gongtao Fan, Hongwei Wang, Chang Xu, Zhigang Xiao
Atomic nuclei and dense nucleonic matter in neutron stars exhibit short-range correlations (SRCs), where nucleons form temporally correlated pairs in close proximity beyond mean-field approximation. It is essential to make precision measurement of the fraction of SRC since it carries the signature of underlying quark dynamics in nuclear medium. In this article, we present the first high-precision measurement of neutron-proton bremsstrahlung γ -ray emission from the symmetric Sn 124 + Sn 124 reactions at 25 MeV/u. From the observed spectral hardening, the precise SRC fraction in the Sn 124 nucleus is extracted to be ( 20 ± 3 ) % . This result provides a statistically unambiguous evidence of SRCs and demonstrates that low-energy heavy-ion collisions offer an approach to studying nuclear structure in connection with quark-level dynamics.