Electromagnetic form factors of Λ b in the Bethe-Salpeter equation approach

The heavy baryon ${\mathrm{\ensuremath{\Lambda}}}_{b}$ is regarded as composed of a heavy quark and a scalar diquark which has good spin and isospin quantum numbers. In this picture, we calculate the electromagnetic form factors of ${\mathrm{\ensuremath{\Lambda}}}_{b}$ in the Bethe-Salpeter equation approach in the spacelike region. We find that the shapes of the electromagnetic form factors of ${\mathrm{\ensuremath{\Lambda}}}_{b}$ are similar to those of $\mathrm{\ensuremath{\Lambda}}$, with a peak at $\ensuremath{\omega}=1$ (for the magnetic form factor) and $\ensuremath{\omega}\ensuremath{\simeq}1.1$ (for the electric form factor)($\ensuremath{\omega}={v}^{\ensuremath{'}}\ifmmode\cdot\else\textperiodcentered\fi{}v$ is the velocity transfer between the initial state (with velocity $v$) and the final state (with velocity ${v}^{\ensuremath{'}}$) of ${\mathrm{\ensuremath{\Lambda}}}_{b}$), but the amplitudes are much smaller than those of $\mathrm{\ensuremath{\Lambda}}$.