ATLAS Detector Simulation in the Integrated Simulation Framework applied to the W Boson Mass Measurement

One of the cornerstones for the success of the ATLAS experiment at the Large Hadron Collider (LHC) is a very accurate Monte Carlo detector simulation. However, a limit is being reached regarding the amount of simulated data which can be produced and stored with the computing resources available through the worldwide LHC computing grid (WLCG). The Integrated Simulation Framework (ISF) is a novel approach to detector simula- tion which enables a more efficient use of these computing resources and thus allows for the generation of more simulated data. Various simulation technologies are combined to allow for faster simulation approaches which are targeted at the specific needs of in- dividual physics studies. Costly full simulation technologies are only used where high accuracy is required by physics analyses and fast simulation technologies are applied everywhere else. As one of the first applications of the ISF, a new combined simulation approach is developed for the generation of detector calibration samples used in the W boson mass measurement. The precise measurement of the W boson mass is crucial for testing the validity of the Standard Model (SM) of particle physics. With a targeted relative error of less than 10−4 for the measurement with the ATLAS detector, billions of simulated collision events are required. Using the flexibility of the ISF, an outstanding agreement with full Geant4 simulation is achieved for the simulation of the crucial lepton observables in Z → ee events. File sizes which are 2 times smaller and execution speeds which are about 5 times faster than traditional Geant4 simulation approaches illustrate that an important step towards the large-scale Monte Carlo production for the W boson mass measurement is achieved through using the ISF.