Search for single-top production in ep collisions at HERA

TL;DR

This study searched for single-top quark production in electron-proton collisions at HERA using the ZEUS detector, aiming to detect signals from both leptonic and hadronic W decay channels, but found no evidence of such production.

Contribution

First search for single-top production in ep collisions at HERA constraining FCNC couplings with new limits from ZEUS data.

Findings

No evidence for single-top production was observed.

The results set new limits on FCNC t-u-gamma couplings.

A substantial region of FCNC parameter space is excluded.

Abstract

A search for single-top production, ep --> etX, has been made with the ZEUS detector at HERA using an integrated luminosity of 130.1 pb-1. Events from both the leptonic and hadronic decay channels of the W boson resulting from the decay of the top quark were sought. For the leptonic mode, the search was made for events with isolated high-energy leptons and significant missing transverse momentum. For the hadronic decay mode, three-jet events in which two of the jets had an invariant mass consistent with that of the W were selected. No evidence for top production was found. The results are used to constrain single-top production via flavour-changing neutral current (FCNC) transitions. The ZEUS limit excludes a substantial region in the FCNC t-u-gamma coupling not ruled out by other experiments.