Search for first-generation leptoquarks in [ital [bar p]p] collisions at [radical][ital s] =1. 8 TeV

We present results of a search for a first-generation leptoquark [ital scrS][sub 1] in [ital [bar p]p] collisions at [radical][ital s] =1.8 TeV at the Fermilab Tevatron. Using 4.05 pb[sup [minus]1] of data collected during the 1988--1989 CDF run, we have searched for evidence of [ital scrS][sub 1][ital scr[bar 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 [ital Z][sup 0] decay. No events were found in the signal region. Assuming a short lived scalar leptoquark with Yukawa coupling strength [lambda][approx gt]2[times]10[sup [minus]7], we exclude [sigma][beta][sup 2][gt]55(4.0) pb at 95% C.L. for [ital M][sub [ital s][ital c][ital r][ital S]]=45(125) GeV/[ital c][sup 2]. Using a Monte Carlo prediction for [sigma]([ital [bar p]p][r arrow][ital scrS][sub 1][ital scr[bar S]1]+[ital X]), we exclude [ital M][sub [ital s][ital c][ital r][ital S]][lt]113(80) GeV/[ital c][sup 2] for [beta]=100(50)%.