A search for resonance decays to lepton+jet at HERA and limits on leptoquarks

TL;DR

This study searched for narrow resonances decaying into lepton+jet at HERA, setting limits on leptoquark masses and couplings, with no evidence of such resonances found.

Contribution

It provides new limits on leptoquark masses and couplings using HERA data, extending previous constraints up to 400 GeV.

Findings

No resonance evidence was observed.

Leptoquark masses up to 290 GeV are excluded for a coupling of 0.1.

Limits also apply to R-parity-violating squarks.

Abstract

A search for narrow-width resonances that decay into electron+jet or neutrino+jet has been performed with the ZEUS detector at HERA operating at center-of-mass energies of 300 and 318 GeV. An integrated e+p luminosity of 114.8 pb-1 and e-p luminosity of 16.7 pb-1 were used. No evidence for any resonance was found. Limits were derived on the Yukawa coupling as a function of the mass of a hypothetical resonance that has arbitrary decay branching ratios into electron+quark or neutrino+quark. These limits also apply to squarks predicted by R-parity-violating supersymmetry. Limits for the production of leptoquarks described by the Buchmuller-Ruckl-Wyler model were also derived for masses up to 400 GeV. For Yukawa coupling of 0.1, leptoquark masses up to 290 GeV are excluded.