  We employ time- and angle-resolved photoemission spectroscopy to study the
spin- and valley-selective photoexcitation and dynamics of free carriers at the
K and K' points in singly-oriented single layer WS$_2$/Au(111). Our results
reveal that in the valence band maximum an ultimate valley polarization of free
holes of 84$\,$% can be achieved upon excitation with circularly polarized
light at room temperature. Notably, we observe a significantly smaller valley
polarization for the photoexcited free electrons in the conduction band
minimum. Clear differences in the carrier dynamics between electrons and holes
imply intervalley scattering processes into dark states being responsible for
the efficient depolarization of the excited electron population.
