We present results of a search for a first-generation leptoquark ${\mathcal{S}}_1$ in $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{}$ TeV at the Fermilab Tevatron. Using 4.05 ${\mathrm{pb}}^{-1\mathrm{}}$ of data collected during the 1988-1989 CDF run, we have searched for evidence of ${\mathcal{S}}_1{\overline{\mathcal{S}}}_1$ production assuming that each leptoquark decays to an electron+quark pair with a branching ratio $\beta$. Three events with two high energy electrons and two high energy jets were found, but are consistent with $Z^0$ decay. No events were found in the signal region. Assuming a short lived scalar leptoquark with Yukawa coupling strength $\lambda \gtrsim 2\times {10}^{-7\mathrm{}}$, we exclude $\sigma {\beta }^2>55\mathrm{}\left(4.0\right)\mathrm{}$ pb at 95% C.L. for $M_{\mathcal{S}}=45\mathrm{}\left(125\right)\mathrm{}$ GeV/${\mathit{c}}^2$. Using a Monte Carlo prediction for $\sigma (\overline{p}p\to {\mathcal{S}}_1{\overline{\mathcal{S}}}_1+X)$, we exclude $M_{\mathcal{S}}<113\mathrm{}\left(80\right)\mathrm{}$ GeV/${\mathit{c}}^2$ for $\beta =100\mathrm{}\left(50\right)\%$.

• Received 5 April 1993

DOI:https://doi.org/10.1103/PhysRevD.48.R3939