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The shapes of cluster central galaxies are not randomly oriented, but rather exhibit coherent alignments with the shapes of their parent clusters as well as with the surrounding large-scale structures. In this work, we aim to identify the galaxy and cluster quantities that most strongly predict the central galaxy alignment phenomenon among a large parameter space with a sample of 8237 clusters and 94 817 members within 0.1 < z < 0.35, based on the red-sequence Matched-filter Probabilistic Percolation cluster catalogue constructed from the Sloan Digital Sky Survey. We first quantify the alignment between the projected central galaxy shapes and the distribution of member satellites, to understand what central galaxy and cluster properties most strongly correlate with these alignments. Next, we investigate the angular segregation of satellites with respect to their central galaxy major axis directions, to identify the satellite properties that most strongly predict their angular segregation. We find that central galaxies are more aligned with their member galaxy distributions in clusters that are more elongated and have higher richness, and for central galaxies with larger physical size, higher luminosity and centring probability, and redder colour. Satellites with redder colour, higher luminosity, located closer to the central galaxy, and with smaller ellipticity show a stronger angular segregation towards their central galaxy major axes. Finally, we provide physical explanations for some of the identified correlations, and discuss the connection to theories of central galaxy alignments, the impact of primordial alignments with tidal fields, and the importance of anisotropic accretion.

This thesis presents work towards the first measurement of the mass of the W boson (m_W) at ATLAS at the Large Hadron Collider using √s = 7 TeV collision data taken in 2011. The electron energy calibration is presented, including a detailed study of the linearity of the ATLAS electromagnetic calorimeter. Separately, the measurement of the W boson recoil is calibrated using Z boson events. Recoil corrections for the underlying event, pileup, recoil magnitude resolution, recoil angular resolution and recoil response mismodelling are determined, with statistical uncertainties on these corrections corresponding to an estimated uncertainty on m_W of 3.9 MeV. The corrections for calorimeter non-linearity and recoil modelling improve the description of the data, though systematic biases remain. To achieve a precision commensurate with the statistics of the data, these biases will need to be understood.