  Studies of Majorana bound states in semiconducting nanowires frequently
neglect the orbital effect of magnetic field. Systematically studying its role
leads us to several conclusions for designing Majoranas in this system.
Specifically, we show that for experimentally relevant parameter values orbital
effect of magnetic field has a stronger impact on the dispersion relation than
the Zeeman effect. While Majoranas do not require a presence of only one
dispersion subband, we observe that the size of the Majoranas becomes
unpractically large, and the band gap unpractically small when more than one
subband is filled. Since the orbital effect of magnetic field breaks several
symmetries of the Hamiltonian, it leads to the appearance of large regions in
parameter space with no band gap whenever the magnetic field is not aligned
with the wire axis. The reflection symmetry of the Hamiltonian with respect to
the plane perpendicular to the wire axis guarantees that the wire stays gapped
in the topologically nontrivial region as long as the field is aligned with the
wire.
