Measurement of Single-top Quark Production with the ATLAS Detector

TL;DR

This paper reports the measurement of single-top quark production cross-sections at 7 TeV using ATLAS data, testing the Standard Model and probing for new physics through various analysis techniques.

Contribution

It provides the first measurement of the single-top t-channel cross-section and sets limits on Wt associated production using neural network and cut-based methods.

Findings

Measured t-channel cross-section: 90 +32 -22 pb, consistent with Standard Model.

Set a limit on Wt production: < 39.1 pb, about 2.5 times the SM expectation.

Demonstrated the effectiveness of neural network approaches in top-quark analyses.

Abstract

Single-top production has been studied with the ATLAS detector using 0.7 fb-1 of 2011 data recorded at 7 TeV center-of-mass energy. The measurement of electroweak production of top-quarks allows probes of the Wtb vertex and a direct measurement of the CKM matrix element |V_tb|. It is also expected to be sensitive to new physics such as flavor changing neutral currents or heavy W production. The t-channel cross-section measurements are performed using both a cut-based and neural network approach, while a cut-based selection in the dilepton channel is used to derive a limit on the associated (Wt) production. An observed cross-section of 90 +32 -22 pb (65 +28 -19 pb expected) is obtained for the t-channel, which is consistent with the Standard Model expectation. For the Wt production, an observed limit of < 39.1 pb (40.6 pb expected) is derived, which corresponds to about 2.5 times the Standard Model expectation.