Bremsstrahlung Gamma Ray as a Probe of Short-Range Correlations in Nuclei

摘要: The nucleons in nuclei  form temporally correlated pairs in close proximity, called short range correlation (SRC), which  plays a crucial role in understanding nuclear structure and the fundamental properties of dense nuclear matter. The consequence of SRC on heavy-ion collisions (HICs) has remained unexplored until now. In this paper, we identify neutron-proton bremsstrahlung γ-ray emission from HICs as a new indicator of SRC in nuclei. By observing the hardening of the bremsstrahlung γ-ray spectrum, which results from the increase of high-momentum components above the Fermi surface in nucleon momentum distributions, we precisely determine the SRC fraction in nuclei to be (21±7)% at 3σ confidence levels.  Our experiment identifies the first direct and accurate signature of SRC in low-energy HICs, providing a new method to study the parton momentum distribution of nucleons in nuclei.