New H1 results on isolated leptons and missing pt at HERA

TL;DR

This paper reports on the analysis of isolated leptons and missing transverse momentum events at HERA, showing a slight excess over Standard Model predictions at high hadronic transverse momentum, based on data from 1994 to 2005.

Contribution

The study provides new H1 results on isolated leptons and missing pt, including data from the HERA II phase, and compares observed events with Standard Model predictions.

Findings

Observed events slightly exceed SM predictions overall.

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

No excess observed in e- p data at high transverse momentum.

Abstract

The search for events containing isolated leptons (electrons or muons) and missing transverse momentum produced in $e^{\pm}p$ collisions is performed with the H1 detector at HERA in the period 1994--2005. The analysed data sample corresponds to an integrated luminosity of 279 pb$^{-1}$, which includes 53 pb$^{-1}$ of $e^{+}p$ data and 107 pb$^{-1}$ of $e^{-}p$ data from the new HERA~II phase. A total of 40 events are observed in the data, compared to a Standard Model (SM) prediction of 34.3 $\pm$ 4.8. At large hadronic transverse momentum $P_{T}^{X} >$ 25 GeV, a total of 17 events are observed compared to 9.0 $\pm$ 1.5 predicted by the SM. In this region, 15 events are observed in the $e^{+}p$ data compared to a SM prediction of 4.6 $\pm$ 0.8, whereas in the $e^{-}p$ data 2 events are observed compared to a SM prediction of 4.4 $\pm$ 0.7.