Exploration of trace anomaly contribution to proton mass based on light vector meson photoproduction

Abstract In the quantum chromodynamics, the mass source of the proton is decomposed into four parts by the energy momentum tensor: quark energy term, gluon energy term, quark mass term and trace anomaly term. And the trace anomaly term is the most crucial contribution for studying the internal structure of the proton. In this work, under the definition of the vector meson dominant model, the trace anomaly contribution of the proton is extracted from the experimental data of light vector mesons $$\rho $$ ρ , $$\omega $$ ω and $$\phi $$ ϕ photoproduction at the near-threshold, which are ( $$0.53\pm 0.15$$ 0.53 ± 0.15 ) $$\%$$ % , ( $$1.47\pm 0.48$$ 1.47 ± 0.48 ) $$\%$$ % and ( $$2.73\pm 0.54$$ 2.73 ± 0.54 ) $$\%$$ % , respectively. Further, combined with the results extracted from the heavy vector meson $$J/\psi $$ J / ψ photoproduction, the distribution of the trace anomaly contribution with the vector meson mass is given for the first time. These results may provide important theoretical information for determining the range of the trace anomaly contribution and for further understanding the origin of the proton mass.