Saverio D'Auria (University of Glasgow (GB))
At the Large Hadron Collider accelerator beam halo cleaning losses on the upstream collimators, or proton collisions with residual gas in the beam pipe can create particle showers that have sufficient energy to reach the ATLAS detector. In some cases the beam-induced particles may mimic physics objects in the calorimeter and as such can create a source of background in the physics analyses. The beam-induced particle showers can also typically result in increased occupancies in the silicon tracker, which may impact on detector operation and read-out. Such beam-induced backgrounds have been carefully studied throughout 2011 and 2012 data taking and the characteristic topologies and timing of the background events have been exploited to develop tools that can identify, study and ultimately mitigate the backgrounds in the physics analysis. Using these identification tools, a significant increase in the rate of the beam-induced backgrounds reaching ATLAS has been observed in 2015 data taking. We present studies of the increase in beam-induced backgrounds observed in LHC run II and compare the observed rates with those calculated from detailed simulations of the accelerator.
ATLAS Collaboration (CERN)