Search for first Generation Leptoquarks in the Electron-Neutrino Channel

The D0 Collaboration

Contact Persons: Alexis Cothenet, Marie-Claude Cousinou, Greg Landsberg

A search for first generation leptoquark pairs in p pbar collisions at the Tevatron is presented using D0 data with an integrated luminosity of 121 pb. The case where one of the 2 leptoquarks decays in an electron and a quark and the other in a neutrino and a quark is considered. The final state consists in an electron, at least 2jets and missing transverse energy. The main backgrounds are the W production, when the W decays in an electron and a neutrino and an instrumental background coming out from QCD events with at least 3 jets when a jet has a high electromagnetic fraction and fake transverse missing energy is created by some jets energy mis-measurements. A smaller background associated to the top production is also considered. No evidence for leptoquark production is found. Assuming a branching ratio of 0.5 for the decay mode searched for, an upper limit of 156 GeV of the leptoquark mass at 95% Confidence Level is given.

A detailed description is available as Dě note 4226 (restricted access; non-D0-speakers, please contact the D0 NP Convenors).

St distribution for MEt>30 GeV for data (points) and total background (histogram). The hashed area indicates the statistical uncertainty on the total background.

Upper 95% C.L. limit on the cross-section times branching fraction as a function of the leptoquark mass (squares). The NLO theoretical cross-sections are plotted for different renormalization and factorisation scale factors: Mlq (full line), Mlq/2 and 2Mlq (dashed lines).

95% C.L. lower limit on leptoquark mass (squares) as a function of beta=BR(LQ->eq).

95% C.L. lower limits on the mass of first generation leptoquarks as a function of beta=BR(LQ->eq) from a combination with the search in the di-electron channel.

Volker Buescher
Last modified: Wed Sep 10 10:42:02 CDT 2003