  We study the effects of spin-orbit coupling on the magnetoconductivity in
diffusive cylindrical semiconductor nanowires. Following up on our former study
on tubular semiconductor nanowires, we focus in this paper on nanowire systems
where no surface accumulation layer is formed but instead the electron wave
function extends over the entire cross section. We take into account the
Dresselhaus spin-orbit coupling resulting from a zinc-blende lattice and the
Rashba spin-orbit coupling, which is controlled by a lateral gate electrode.
The spin relaxation rate due to Dresselhaus spin-orbit coupling is found to
depend neither on the spin density component nor on the wire growth direction
and is unaffected by the radial boundary. In contrast, the Rashba spin
relaxation rate is strongly reduced for a wire radius that is smaller than the
spin precession length. The derived model is fitted to the data of
magnetoconductance measurements of a heavily doped back-gated InAs nanowire and
transport parameters are extracted. At last, we compare our results to previous
theoretical and experimental studies and discuss the occurring discrepancies.
