ATLAS Inner Detector alignment and analysis of the Wtb vertex structure with single top quarks

This thesis can be divided in to two different parts: one is about the alignment of the ATLAS Inner Detector, and the other one about studies of the Wtb vertex using single top quark events. The first part presents the techniques used to align the ATLAS ID and the upgrades implemented in the alignment framework during LHC Run-II. Dynamic displacements and deformations of ID subdetectors take place during the data taking, compromising the quality of the recorded data. The two more relevant movements or deformations of the ID are a vertical displacement of the Pixel and the bowing of the IBL. Time-dependent corrections have been implemented in the automatic alignment performed at the Calibration Loop each time a new run is recorded. These dynamic corrections are able to correct for both misalignments. It removes the impact that these time-dependent misalignments have in the data. Despite of the harsher conditions of the ID during LHC Run-II, thanks to the upgrades performed in the alignment framework, a similar alignment performance to the one of Run-I has been achieved. Finally, in order to profit the computing resources of Tier-0, a new alignment machinery has been developed allowing the sending of alignment jobs to the Tier-0 system. The second part covers the studies performed about the structure of the Wtb vertex using single top quark events produced in the t-channel. The analysis uses 20.2 ifb of ATLAS data from 2012 at a centre of mass energy of 8 TeV. The selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, of which one is tagged as a b-jet. A cut-based analysis has been developed in order to discriminate the signal events from the background contributions. Several polarization observables have been measured with this events. The polarization observables are measured from asymmetries of various angular distributions unfolded at parton level. Most of the angular distributions have been unfolded with unfolding correction based on Standard Model simulations. In the other hand, for the extraction of three asymmetries, model-independent corrections derived through an interpolation method developed for this analysis have been used. These asymmetries have been used to set limits on the values of Wtb anomalous couplings. Limits on the real and imaginary part of the anomalous coupling gR have been set, using several measured asymmetries. The extracted limits on the imaginary part of gR improve the most recently published limits. In the other hand, the extracted limit in the real part of gR is not as precise as other published measurements. In both cases, the limits set are compatible with the Standard Model predictions for the real and imaginary part of gR.