Search for First-Generation Scalar and Vector Leptoquarks

TL;DR

This study searches for first-generation scalar and vector leptoquarks in proton-antiproton collisions, setting mass limits based on non-observation, and compares results with theoretical predictions to constrain leptoquark properties.

Contribution

First comprehensive search for first-generation scalar and vector leptoquarks at Fermilab Tevatron, establishing new mass limits and combining multiple channels for improved sensitivity.

Findings

No evidence for leptoquark production was observed.

Set 95% CL lower mass limits for scalar leptoquarks up to 225 GeV/c^2.

Set 95% CL lower mass limits for vector leptoquarks up to 345 GeV/c^2.

Abstract

We describe a search for the pair production of first-generation scalar and vector leptoquarks in the eejj and enujj channels by the D0 Collaboration. The data are from the 1992--1996 ppbar run at sqrt{s} = 1.8 TeV at the Fermilab Tevatron collider. We find no evidence for leptoquark production; in addition, no kinematically interesting events are observed using relaxed selection criteria. The results from the eejj and enujj channels are combined with those from a previous D0 analysis of the nunujj channel to obtain 95% confidence level (C.L.) upper limits on the leptoquark pair-production cross section as a function of mass and of beta, the branching fraction to a charged lepton. These limits are compared to next-to-leading-order theory to set 95% C.L. lower limits on the mass of a first-generation scalar leptoquark of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively. For vector leptoquarks with gauge (Yang-Mills) couplings, 95% C.L. lower limits of 345, 337, and 206 GeV/c^2 are set on the mass for beta=1, 1/2, and 0, respectively. Mass limits for vector leptoquarks are also set for anomalous vector couplings.