Pion gravitational form factors in a relativistic theory of composite particles

Abstract

We extend our relativistic theory of electroweak properties of composite systems to describe simultaneously the gravitational form factors of hadrons. The approach is based on a version of the instant-form relativistic quantum mechanics and makes use of the modified impulse approximation. We exploit the general method of the relativistic invariant parametrizaton of local operators to write the energy-momentum tensor of a particle with an arbitrary spin. We use the obtained results to calculate the gravitational form factors of the pion assuming point-like constituent quarks. All but one parameters of our first-principle model were fixed previously in works on electromagnetic form factors. The only free parameter, Dq, is a characteristic of the gravitational form factor of a constituent quark. The derived form factors of the pion satisfy the constraints given by the general principles of the quantum field theory of hadron structure. The calculated gravitational form factors and gravitational mean-square radius are in a good agreement with known results. The results demonstrate self-consistency of a common relativistic approach to electromagnetic and gravitational form factors of pion.

K0 and K+ -meson electromagnetic form factors: A nonperturbative relativistic quark model versus experi

“…Further studies within this approach included calculations of electromagnetic properties of other light mesons [14,15], as well as preliminary studies of the πmeson gravitational form factor [16] and a generalization of the infrared-ultraviolet π-meson link to gauge theories beyond QCD [17], in a general agreement with available lattice results. However, one of parameters of the model for K mesons remained poorly constrained because of the low precision of the experimental determination of K + charge radius, r 2 K + 1/2 .…”