  We present an improved determination of the strange quark and anti-quark
parton distribution functions of the proton by means of a global QCD analysis
that takes into account a comprehensive set of strangeness-sensitive
measurements: charm-tagged cross sections for fixed-target neutrino-nucleus
deep-inelastic scattering, and cross sections for inclusive gauge-boson
production and $W$-boson production in association with light jets or charm
quarks at hadron colliders. Our analysis is accurate to next-to-next-to leading
order in perturbative QCD where available, and specifically includes
charm-quark mass corrections to neutrino-nucleus structure functions. We find
that a good overall description of the input dataset can be achieved and that a
strangeness moderately suppressed in comparison to the rest of the light sea
quarks is strongly favored by the global analysis.

High Energy Physics - Phenomenology;High Energy Physics - Experiment;High Energy Physics - Lattice;Nuclear Theory