Events with an Isolated Lepton and Missing Transverse Momentum and Measurement of W Production at HERA

TL;DR

This paper reports on a search for events with isolated leptons and missing transverse momentum at HERA, measuring W boson production and comparing observed data with Standard Model predictions over a broad dataset.

Contribution

The study provides a comprehensive measurement of W production at HERA, including new event counts at high transverse momentum and an updated cross section measurement.

Findings

Observed event yields agree with Standard Model predictions.

Measured W production cross section is consistent with theoretical expectations.

Identified excess of events at high hadronic transverse momentum in e+p data.

Abstract

A search for events containing an isolated electron or muon and missing transverse momentum produced in ep collisions is performed with the H1 and ZEUS detectors at HERA. The data were taken in the period 1994-2007 and correspond to an integrated luminosity of 0.98 fb^-1. The observed event yields are in good overall agreement with the Standard Model prediction, which is dominated by single W production. In the e+p data, at large hadronic transverse momentum PtX >25 GeV, a total of 23 events are observed compared to a prediction of 14.0 \pm 1.9. The total single W boson production cross section is measured as 1.06 \pm 0.16 (stat.) \pm 0.07 (sys) pb, in agreement with an SM expectation of 1.26 \pm 0.19 pb.