Miles Wu (University of Chicago (US))
This talk presents the observation and differential measurement of collinear W emission from jets with high transverse momentum using the ATLAS detector from pp collisions at a center-of-mass energy of 8 TeV. The measurement is performed in the muon decay channel and the cross-section is reported as a function of the distance between the muon and the closest jet, since a notable signature of this process is a W close to an energetic jet. This particular topology, made accessible by the high energies and large data sample of the LHC, has never been explicitly studied before and provides a test of theoretical QCD and electroweak models. The measured differential cross-section is compared with both multi-leg (Sherpa and Alpgen) and LO with weak showering (Pythia 8) calculations. Understanding this process is also relevant for searches for new physics that involves boosted tops, where collinear W emission may be an important background as they share a similar final state.