  The interpretation of cosmic antiproton flux measurements from space-borne
experiments is currently limited by the knowledge of the antiproton production
cross-section in collisions between primary cosmic rays and the interstellar
medium. Using collisions of protons with an energy of 6.5 TeV incident on
helium nuclei at rest in the proximity of the interaction region of the LHCb
experiment, the ratio of antiprotons originating from antihyperon decays to
prompt production is measured for antiproton momenta between 12 and 110 GeV/c.
The dominant antihyperon contribution, namely $\bar{\Lambda} \to \bar{p} \pi^+$
decays from promptly produced $\bar{\Lambda}$ particles, is also exclusively
measured. The results complement the measurement of prompt antiproton
production obtained from the same data sample. At the energy scale of this
measurement, the antihyperon contributions to antiproton production are
observed to be significantly larger than predictions of commonly used hadronic
production models.
