Search for first-generation leptoquarks at HERA

TL;DR

This study conducted a comprehensive search for first-generation leptoquarks at HERA using electron-proton collision data, but found no evidence, setting new limits on their possible masses and couplings.

Contribution

It provides the first combined analysis of HERA data to set constraints on first-generation leptoquark properties within a specific theoretical model.

Findings

No evidence of leptoquark signals was observed.

Leptoquarks with coupling lambda=0.3 are excluded up to 699 GeV.

The analysis extends previous limits on leptoquark masses and couplings.

Abstract

A search for first-generation leptoquarks was performed in electron-proton and positron-proton collisions recorded with the ZEUS detector at HERA in 2003-2007 using an integrated luminosity of 366 pb^-1. Final states with an electron and jets or with missing transverse momentum and jets were analysed, searching for resonances or other deviations from the Standard Model predictions. No evidence for any leptoquark signal was found. The data were combined with data previously taken at HERA, resulting in a total integrated luminosity of 498 pb^-1. Limits on the Yukawa coupling, lambda, of leptoquarks were set as a function of the leptoquark mass for different leptoquark types within the Buchmueller-Rueckl-Wyler model. Leptoquarks with a coupling lambda=0.3 are excluded for masses up to 699 GeV.