Magnetic moment of the ρ meson in instant-form relativistic quantum mechanics

We derive an explicit analytical expression for the magnetic dipole moment of the rho meson, mu(rho), in a relativistic constituent-quark model. We adopt our relativistic approach to composite systems, modified instant-form (mIF) relativistic quantum mechanics (RQM), that we used particularly to construct a unified pi & rho model [Phys. Rev. D 93, 036007 (2016)] describing electroweak properties of light mesons. This model provides a parameter-free calculation to give mu(rho) = 2.16 +/- 0.03 [e/2M(rho)] which is in accordance with the conventional experimental data. The magnetic, quadrupole, and charge form factors also are derived and presented. We consider the small uncertainty of our value of the magnetic moment as one of the undoubted advantages of the method. A comparison is made with recent lattice QCD results and previous calculations using a variety of methods.