First measurement of the t-channel single top production in pp collisions at √s = 5.02$ TeV with the ATLAS experiment

A measurement of single top quark production t−channel cross-section in proton-proton collisions at an energy in the centre-of-mass of √s=5.02 TeV with 257 pb−1 of data collected by the ATLAS experiment at LHC is reported. This analysis applies event selections to identify t−channel single top candidate events decaying semi-leptonically. Selected events are then used to train a Boosted Decision Tree (BDT) to optimize signal versus background separation. A Profile-Likelihood (PL) fit is performed to measure the total cross-section σ(tq+t¯q) and the ratio between the top quark (tq), and anti-top quark (t¯q) cross-sections Rt. The analysis uses forward jets to enhance the t−channel significance (jet η<4.0). Measured values of the cross-section σ(tq+t¯q)=6.6+4.3−4.0(stat.) +4.4−3.6(syst.) and of the ratio Rt=2.74+1.44−0.83(stat.) +1.04−0.29(syst.) are well in agreement with Standard Model (SM) predictions.