Searches for First Generation Leptoquark Pair Production in pbar-p Collisions at D0

TL;DR

This study searched for first generation scalar leptoquark pairs in proton-antiproton collisions at the Tevatron, setting mass limits and ruling out certain interpretations of HERA high-Q^2 event excesses.

Contribution

The paper provides the first comprehensive search combining multiple channels for first generation leptoquarks at the Tevatron, establishing new mass limits and constraining theoretical models.

Findings

No leptoquark candidates observed.

Set 95% CL lower mass limits of 225, 204, and 79 GeV/c^2 for different beta values.

Excluded leptoquark interpretations of HERA high-Q^2 events below 200 GeV/c^2 for beta > 0.4.

Abstract

We have searched for the pair production of first generation scalar leptoquarks using the full data set (123 pb**-1) collected with the D0 detector at the Fermilab Tevatron during 1992-1996. We observe no candidates, consistent with the expected background. We combine these new results from the ee + jets and enu + jets channels with the published nunu + jets result to obtain a 95% CL upper limits on the LQ pair production cross section as a function of mass and beta, the branching ratio to a charged lepton and a quark. Comparing to the NLO theory predictions, we set 95% CL lower limits on the LQ mass of 225, 204, and 79 GeV/c**2 for beta=1, 1/2, and 0, respectively. The results of this analysis rule out an interpretation of the excess of high Q**2 events at HERA as leptoquarks with LQ mass below 200 GeV/c**2 for values of beta > 0.4.