  We investigate possible effects of correlations between stopped nucleons on
higher order proton cumulants at low energy heavy-ion collisions. We find that
fluctuations of the number of wounded nucleons $N_{\mathrm{part}}$ lead to
rather nontrivial dependence of the correlations on the centrality; however,
this effect is too small to explain the large and positive four-proton
correlations found in the preliminary data collected by the STAR collaboration
at $\sqrt{s}=7.7$ GeV. We further demonstrate that, by taking into account
additional proton clustering, we are able to qualitatively reproduce the
preliminary experimental data. We speculate that this clustering may originate
either from collective/multi-collision stopping which is expected to be
effective at lower energies or from a possible first-order phase transition, or
from (attractive) final state interactions. To test these ideas we propose to
measure a mixed multi-particle correlation between stopped protons and a
produced particle (e.g. pion, antiproton).
