  The cumulants of baryon multiplicity distribution in relativistic heavy-ion
collisions (HICs) have attracted considerable attention recently. It has been
conjectured that they may serve as a promising observable to detect the
critical end point in the QCD phase diagram, while the cumulants in HICs at
intermediate energies have not been widely studied to date. How to interpret
the cumulants data at intermediate energies and compare with the data at
relativistic energies is now being actively discussed. Both meam-field
potential and clustering are highly important to HICs at intermediate energies.
In this talk, we discuss these effects on the cumulant ratios of baryon number
distributions in Au+Au collisions at beam energies of 1.23 GeV$/$nucleon which
have been currently performed by the HADES Collaboration at GSI. Within the
newest version of the ultrarelativistic quantum molecular dynamics (UrQMD)
model, calculations with different mean field potentials as well as without
mean field potential are performed. It is found that the mean field potential
enhances fluctuations in the momentum space during the expanding stage,
especially in a small rapidity acceptance window. The enhancement of cumulant
ratios for free protons is suppressed compared with that for all baryons.
