Pseudorapidity distributions of charged particles produced inp¯pinteractions ass=630and 1800 GeV

We present measurements of the pseudorapidity ($\eta$) distribution of charged particles ($\frac{d{N}_{\mathrm{ch}}}{d\eta }$) produced within $\left|\eta \right|\le 3.5$ in proton-antiproton collisions at $\sqrt{s}$ of 630 and 1800 GeV. We measure $\frac{d{N}_{\mathrm{ch}}}{d\eta }$ at $\eta =0\mathrm{}$ to be 3.18±0.06(stat)±0.10(syst) at 630 GeV, and 3.95±0.03 (stat)±0.13(syst) at 1800 GeV. Many systematic errors in the ratio of $\frac{d{N}_{\mathrm{ch}}}{d\eta }$ at the two energies cancel, and we measure 1.26±0.01±0.04 for the ratio of $\frac{d{N}_{\mathrm{ch}}}{d\eta }$ at 1800 GeV to that at 630 GeV within $\left|\eta \right|\le 3$. Comparing to lower-energy data, we observe an increase faster than $\ln \mathrm{}\left(s\right)\mathrm{}$ in $\frac{d{N}_{\mathrm{ch}}}{d\eta }$ at $\eta =0\mathrm{}$.