Using a light-front Hamiltonian with three-quark and three-quark-plus-gluon Fock sectors, the authors extract quark and gluon gravitational form factors and find a proton mass decomposition of 31.5% quark energy, 34.7% gluon field energy, 11.3% quark condensate, and 22.5% trace anomaly at 4 GeV^2.
Photo-production of $\eta_{c,b}$ near Threshold
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We analyze the photo-production of $\eta_{c,b}$ off a proton in the threshold region, in terms of C-odd gluonic correlations in the off-forward proton matrix element. Near threshold, the skewness is large leading to a production amplitude that is dominated by four C-odd twist-3 gluon GPDs. We use the QCD instanton vacuum to estimate these C-odd contributions in the proton. The results are used to estimate the differential cross sections for coherent photo-production of $\eta_{c,b}$ in the threshold region, at current electron facilities.
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Proton Gravitational Structure and Mass Decomposition on the Light Front
Using a light-front Hamiltonian with three-quark and three-quark-plus-gluon Fock sectors, the authors extract quark and gluon gravitational form factors and find a proton mass decomposition of 31.5% quark energy, 34.7% gluon field energy, 11.3% quark condensate, and 22.5% trace anomaly at 4 GeV^2.