Search for pair production of first-generation leptoquarks in pp¯ collisions at s=1.96 TeV

A search for pair production of first-generation leptoquarks (LQ) is performed with data collected by the DØ experiment in pp¯ collisions at s=1.96 TeV at the Fermilab Tevatron Collider. In a sample of data corresponding to ∼1 fb−1 the search has been performed on the final states with two electrons and two jets or one electron, two jets and missing transverse energy. We find our data consistent with standard model expectations. The results are combined with those found in a previous analysis of events with two jets and missing transverse energy to obtain scalar LQ mass limits. We set 95% C.L. lower limits on a scalar LQ mass of 299 GeV, 284 GeV and 216 GeV for β=1, β=0.5 and β=0.02 respectively, where β is the LQ branching ratio in the eq channel. This improves the results obtained with a lower luminosity sample from Run II of the Tevatron. Lower limits on vector LQ masses with different couplings from 357 GeV to 464 GeV for β=0.5 are also set using this analysis.