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Résumé |
Gravitational form factors (GFFs) probe the internal mass distribution and the dynamics of quarks and gluons within the hadron. They are defined from matrix elements of the energy-momentum tensor and encode the momentum, pressure and energy distributions inside hadrons. While lattice QCD offers robust results in Euclidean space, continuum methods such as the Dyson-Schwinger (DSE) and Bethe-Salpeter (BS) approaches formulated directly in Minkowski space allow direct access to real-time observables and to the infrared dynamics relevant for the gluonic contributions.
We compute the pion GFFs from Minkowski-space BS amplitudes and DSE solutions with dressed quarks and gluons, using analytical models constrained by lattice results for the dressed propagators and the quark-gluon vertex, with emphasis on the separation of quark and gluon contributions. Particular attention is given to the pole of the lightest scalar meson, the $\rho$, in the quark-graviton vertex, a structure that a bare energy-momentum insertion leaves out. Momentum conservation and the soft-pion theorem fix the two parameters of the model, so that the GFFs can be confronted with lattice data. |
