1. Graham Sellers Simulations of the beamline and detector regions of the LHC and FP420

2. Particle Backgrounds Main sources of background affecting the detector region Interaction of the beam with gas in the beampipe (beam-gas) Protons interacting with beampipe walls before reaching detector Knowledge of the background is vital to construction and operation of the detector

3. BDSIM Toolkit for simulations Construct a lattice Trace particle trajectories through machine, including interaction with matter Physical geometry of the beamline Individual components Dipoles, Quadrupoles, Drift sections Ability to calculate background levels in the region of the detector

4. Tracking Particles Display of beamline from the ATLAS interaction point to 420m downstream Individual elements shown (dipole elements in blue for example) Track the transportation of specified particles through this region

5. Trajectory of off energy particles Calculate transverse deviation plot (the dispersion) using BDSIM Particles with different momentum loss at the IP follow dispersive trajectories Extremely good agreement with other calculations

6. Current and future work Calculation of the acceptance for different Higgs masses using BDSIM Utilise Geant 4 to simulate proton interactions with matter Determine the contribution from this source of background (this will provide the dominant machine-induced background) Study beam-gas backgrounds