  We investigate the mechanical structure of a spin-1 particle. Introducing
three different frameworks, i.e., the three-dimensional (3D) Breit frame, the
two-dimensional (2D) Breit frame, and the 2D infinite momentum frame
(equivalently the two-dimensional Drell-Yan frame), we scrutinize the 2D and 3D
energy-momentum tensor (EMT) distributions in these frames. We first derive the
EMT distributions in the 2D Breit frame by performing the Abel transformation.
The mass distribution in the 2D Breit frame contains an additional monopole
contribution induced geometrically. The pressure distribution in the 2D Breit
frame also gets an induced monopole structure. When the Lorentz boost is
carried out, the mass distribution in the 2D infinite-momentum frame acquires
the induced dipole term. Similarly, we also have the induced dipole
contributions to the pressure and shear-force densities. We visualize the 2D
mass distributions when the spin-1 particle is polarized along the $x$- and
$z$-axes. We observe that the 2D mass distribution in the infinite momentum
frame exhibit clearly the induced dipole structure when the spin-1 particle is
polarized along the $x$-axis. We also discuss the strong force fields inside a
polarized spin-1 particle.

High Energy Physics - Phenomenology