https://doi.org/10.1140/epjc/s10052-020-8057-9
Regular Article - Theoretical Physics
The origin of proton mass from J/
photo-production data
1
Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
2
University of Chinese Academy of Sciences, Beijing, 100049, China
3
Guangdong Provincial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou, 510006, China
* e-mail: xchen@impcas.ac.cn
Received:
11
April
2020
Accepted:
16
May
2020
Published online:
6
June
2020
The trace of the stress tensor characterizes the transformation of a theory under rescaling. In quantum chromodynamics (QCD), this trace contains contributions from the bare masses of the quarks and also from a purely quantum effect, called the QCD trace anomaly. It affects all masses in the theory. We present an estimation of the QCD trace anomaly from the near-threshold 
photo-production data of the GlueX experiment, at JLab. We apply a vector meson dominance model to describe the photo-production of and a running strong coupling which includes the nonperturbative effects in the low 
region. Despite the large uncertainty, we find that the experimental data favors a small value of the trace anomaly parameter 
. We report the resulting proton mass decompositions at 
and 
.
© The Author(s), 2020
