  We investigate the use of partially twisted boundary conditions in a lattice
simulation with two degenerate flavours of improved Wilson sea quarks. The use
of twisted boundary conditions on a cubic volume (L^3) gives access to
components of hadronic momenta other than integer multiples of 2*pi/L. Partial
twisting avoids the need for new gluon configurations for every choice of
momentum, while, as recently demonstrated, keeping the finite-volume errors
exponentially small for the physical quantities investigated in this letter. In
this study we focus on the spectrum of pseudo scalar and vector mesons, on
their leptonic decay constants and on Z_P, the matrix element of the pseudo
scalar density between the pseudo scalar meson and the vacuum. The results
confirm the momentum shift imposed by these boundary conditions and in addition
demonstrate that they do not introduce any appreciable noise. We therefore
advocate the use of partially twisted boundary conditions in applications where
good momentum resolution is necessary.
