Multi-Leptons with High Transverse Momentum at HERA

TL;DR

This paper analyzes high transverse momentum multi-lepton events at HERA, finding general agreement with the Standard Model but observing some high-energy events in e^+p collisions that exceed expectations.

Contribution

It provides the first detailed measurement of multi-lepton production at HERA, including cross sections and event counts, with a focus on high transverse momentum events.

Findings

Seven high-energy di- and tri-lepton events observed in e^+p collisions.

Measured cross sections align with Standard Model predictions.

No excess events observed in e^-p collisions.

Abstract

Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb^{-1}. The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e^+p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94+-0.17 events are expected. Such events are not observed in e^-p collisions for which 1.19+-0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.