Top quark pair production Cross Section in ATLAS with early data

TL;DR

This paper reports on the measurement of top quark pair production cross section using early ATLAS data at 7 TeV, analyzing candidate events in different channels and estimating backgrounds with data-driven methods.

Contribution

It provides the first measurement of top quark pair production cross section with early LHC data and introduces a data-driven background estimation technique.

Findings

Observation of candidate top quark pair events

Comparison of event properties with Monte Carlo simulations

Data-driven estimation of QCD multi-jet background

Abstract

A search is performed for top quark pairs with early data of ATLAS pp collision taken at {\surd}s = 7 TeV. Several candidate events are observed, in both lepton plus jets and dilepton channels. The properties of these events are described, and compared to the expectations from Monte Carlo simulation. A first study of the backgrounds in the lepton plus jets channel is presented including a data-driven determination of the contribution of QCD multi-jet events.