Machine Induced Experimental Background Conditions in the LHC

The Large Hadron Collider set a new energy record for particle accelerators in late 2009, breaking the previous record held by Tevatron of 2 TeV collision energy. The LHC today operates at a collision energy of 7 TeV. With higher beam energy and intensity, measures have to be taken to ensure optimal experimental conditions and safety of the machine and detectors. Machine induced experimental background can severely reduce the quality of experimental triggers and track reconstruction. In a worst case, the radiation levels can be damaging for some of the subdetectors. The LHC is a particular challenge in this regard due to the vastly different operating conditions of the different experiments. The nominal luminosity varies by four orders of magnitude. The unprecedented stored beam energy and the amount of superconducting elements can make it challenging to protect the accelerator itself as well. In this work we have simulated and measured the machine induced background originating from various sources: the beam colliding with rest-gas, collision residues that are transported between the experiments, and from beam halo impacting on aperture restrictions. The aim of the work has been to get a first complete overview of all background sources, in order to better understand how we can optimise the running conditions for the LHC experiments. We have found that the most important background source is beam-gas background, with an expected background rate towards the experiments for the nominal machine on the order of MHz. Other sources of background have been carefully considered and are found to pose less of a challenge under normal running conditions.