Isolated Leptons and Missing P_{T} at HERA

TL;DR

This paper analyzes isolated leptons and missing transverse momentum in e±p collisions at HERA, combining data from H1 and ZEUS to compare observed events with Standard Model predictions and explore potential new physics signals.

Contribution

It provides a comprehensive analysis of HERA data for isolated leptons and missing P_T, including cross section measurements and a search for single top production, using the full high-energy dataset from 1994 to 2007.

Findings

Observed events are consistent with Standard Model predictions overall.

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

Constraints on single top production and W polarization fractions.

Abstract

The search for events containing isolated leptons (electrons or muons) and missing transverse momentum produced in e^{\pm}p collisions is performed individually and in a common phase space with the H1 and ZEUS detectors at HERA in the period 1994--2007. The analysed H1+ZEUS data sample corresponds to an integrated luminosity of 0.97 fb^{-1}, and composes of the complete high energy data from the HERA programme. A total of 87 events are observed in the data, compared to a Standard Model (SM) prediction of 92.7 \pm 11.2. At large hadronic transverse momentum P_{T}^{X} > 25 GeV in the e^{+}p data, luminosity 0.58 fb^{-1}, 23 data events are observed compared to a SM prediction of 14.6 \pm 1.9. Production cross section measurements of events containing isolated leptons and missing transverse momentum and single W production, as well as W polarisation fractions performed by the H1 Collaboration are also presented. The H1 isolated lepton events are also examined in the context of a search for single top production.