An excitation function of proton rapidity distributions for different
centralities is reported from AGS Experiment E917 for Au+Au collisions at 6, 8,
and 10.8 GeV/nucleon. The rapidity distributions from peripheral collisions
have a valley at midrapidity which smoothly change to distributions that peak
at midrapidity for central collisions. The mean rapidity loss increases with
increasing beam energy, whereas the fraction of protons consistent with
isotropic emission from a thermal source at midrapidity decreases with
increasing beam energy.Comment: 9 pages, 3 figures, 1 table replaced version has figures rotate