The potential scattering of electrons carrying non--zero quanta of the
orbital angular momentum (OAM) is studied in a framework of the generalized
Born approximation, developed in our recent paper by Karlovets \textit{et al.},
Phys. Rev. A. {\textbf 92}, 052703 (2015). We treat these so--called
\textit{twisted} electrons as spatially localized wave--packets. The simple and
convenient expressions are derived for a number of scattering events in
collision of such a vortex electron with a single potential, located at a given
impact parameter with respect to the wave-packet's axis. The more realistic
scenarios are also considered with either localized (mesoscopic) targets or
infinitely wide (macroscopic) ones that consist of the randomly distributed
atoms. Dependence of the electron scattering pattern on a size and on a
relative position of the target is studied in detail for all three scenarios of
the single--potential--, mesoscopic-- and the macroscopic targets made of
hydrogen in the ground 1s state. The results demonstrate that the angular
distribution of the outgoing electrons can be very sensitive to the OAM and to
kinematic parameters of the focused twisted beams, as well as to composition of
the target. Scattering of vortex electrons by atoms can, therefore, serve as a
valuable tool for diagnostic of such beams.Comment: 13 pages, 6 figure
