The production of a W boson in association with “jets” of particles initiated by quarks or gluons (“W+jets” events) is an important signature to test quantum chromodynamics, the theory of strong interactions. A new measurement reported by ATLAS focuses on studying the properties of the jets in a large data sample of W+jets events.
This and similar measurements allow ATLAS to test the newest theoretical calculations of such processes, which promise not less than a break-through in terms of precision predictions. These tests are of paramount importance to improve the accuracy with which the experiments can probe the Higgs boson sector and search for new phenomena.
The analysis features precise studies of the number and properties of the jets produced in association with the W boson, as well as the properties of the entire event. The first figure shows the scalar sum of the transverse momentum of jets, lepton, and missing transverse energy from W decay for events with at least one associated jet. The data compared to several existing theory predictions are shown in the second figure. Modelling deficits, requiring further theoretical improvements, are visible at high scalar sum values, a region of interest for new physics searches.