Search for Leptoquarks and FCNC in e^+ e^- annihilations at $\sqrt{s}=183 GeV$

TL;DR

This paper reports on a search for leptoquarks and flavor-changing neutral currents in electron-positron collisions at 183 GeV, setting new limits on their masses, couplings, and cross-sections based on data from the DELPHI detector at LEP-2.

Contribution

First search for scalar and vector leptoquarks and FCNC processes at this energy, establishing new mass and coupling limits and constraining new physics models.

Findings

Leptoquark masses constrained between 134 and 171 GeV/c^2.

FCNC cross-section limit set at 0.55 pb.

No evidence found for leptoquarks or FCNC processes.

Abstract

A search for events with one jet and at most one isolated lepton used data taken at LEP-2 by the DELPHI detector.These data were accumulated at a center-of-mass energy of 183 GeV and correspond to an integrated luminosity of 47.7 1/pb. Production of single scalar and vector leptoquarks was searched for. Limits at 95% confidence level were derived on the masses (ranging from $134 GeV/c^2$ to $171 GeV/c^2$ for electromagnetic type couplings) and couplings of the leptoquark states.A search for top-charm flavour changing neutral currents($e^+ e^- \to \bar t c$ or charge conjugate) used the semileptonic decay channel. A limit on the flavour changing cross-section via neutral currents was set at 0.55pb (95% confidence level).