  We present ab-initio calculations of the electronic differential energy
transfer (DET) cross-sections for antiprotons with energies between $3$keV and
$1$MeV interacting with helium. By comparison with simulations employing the
mean-field description based on the single-active electron approximation we are
able to identify electron correlation effects in the stopping and straggling
cross sections. Most remarkably, we find that straggling exceeds the celebrated
Bohr straggling limit when correlated shake-up processes are included.
