W Production and the Search for Events with an Isolated High-Energy Lepton and Missing Transverse Momentum at HERA

TL;DR

This paper reports a search for W boson production in electron-proton collisions at HERA, observing a few candidate events consistent with the Standard Model and setting upper limits on production cross sections.

Contribution

It provides new measurements and limits on W boson production and decay channels at HERA, including a comparison with previous observations by H1.

Findings

Observed 3 W→eν candidate events consistent with SM

Set upper limit of 3.3 pb on W production cross section

Results align with Standard Model predictions

Abstract

A search for the leptonic decays of W bosons produced in the reaction e^+ p\to e^+ W^\pm X at a centre-of-mass energy of 300 GeV has been performed with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1 . Three events consistent with W\to e\nu decay are found, giving a cross section of 0.9 +1.0 -0.7 \pm 0.2 pb, in good agreement with the Standard Model prediction. The corresponding 95% C.L. upper limit on the cross section is 3.3 pb. A search for the decay W\to \mu\nu has a smaller selection efficiency and yields no candidate events. Limits on the cross section for W production with large hadronic transverse momentum have been obtained. A search for high-transverse-momentum isolated tracks in events with large missing transverse momentum yields results in good agreement with Standard Model expectations, in contrast to a recent report by the H1 collaboration of the observation of an excess of such events.