  In this work, under the framework of vector meson dominance model, the trace
anomaly contribution value inside neutrons are extracted for the first time
based on vector meson photoproduction data. Furthermore, we systematically
compare and analyze the trace anomaly contributions of protons and neutrons.
The results show that the trace anomaly contributions of protons and neutrons
are close, which indirectly confirms that their internal structures and dynamic
properties may have certain similarities. In addition, the main factors
affecting the extraction of the trace anomaly contribution of nucleons are
discussed in detail. This study not only provides a theoretical basis for us to
better understand the source of nucleon mass, but also makes a useful
exploration and discussion on how to extract the trace anomaly contribution of
nucleon more accurately in the future.
