  In a classical plasma the momentum distribution, $n(k)$, decays
exponentially, for large $k$, and the same is observed for an ideal Fermi gas.
However, when quantum and correlation effects are relevant simultaneously, an
algebraic decay, $n_\infty(k)\sim k^{-8}$ has been predicted. This is of
relevance for cross sections and threshold processes in dense plasmas that
depend on the number of energetic particles. Here we present extensive
\textit{ab initio} results for the momentum distribution of the nonideal
uniform electron gas at warm dense matter conditions. Our results are based on
first principle fermionic path integral Monte Carlo (CPIMC) simulations and
clearly confirm the $k^{-8}$ asymptotic. This asymptotic behavior is directly
linked to short-range correlations which are analyzed via the on-top pair
distribution function (on-top PDF), i.e. the PDF of electrons with opposite
spin. We present extensive results for the density and temperature dependence
of the on-top PDF and for the momentum distribution in the entire momentum
range.
