Measurement of Single-top t-channel Production Using ATLAS Data

This document reports the measurement of the single-top t-channel cross-section using data from the ATLAS detector, located at the Large Hadron Collider on the border of France and Switzerland. The data used were collected during the first half of 2011, from proton-proton collisions with a 7 TeV center-of-mass collision energy. Single-top is electroweak top-quark production and t-channel is one of the standard model production modes. To isolate this production, selections are applied to find events with a similar final state. A cut-based analysis is used to further isolate the signal using a series of selections in several orthogonal kinematic regions. Finally, a statistical analysis is performed to determine the measured cross-section and the CKM matrix element |Vtb|. The cross-section for top and anti-top production is considered separately and the resulting cross-sections are σ t+ = 59 +18 -16 pb for the positive charge channel and σ t- = 33 +13 -12 pb for the negative charge channel. The total measured single-top t-channel cross-section using all kinematic channels in this analysis is 92 +29 -26 pb with an expected cross-section of σ t = 65 +22 -20 pb. The 95% confidence level limit on the standard model |Vtb| value is determined to be |Vtb| > 0.67.