Relative Luminosity Measurement with Timepix3 in ATLAS

The capability of Timepix3 detectors installed in ATLAS to measure luminosity is evaluated. It is described how noisy pixels are identified and excluded. Two different methods for luminosity determination, i.e. cluster counting and thermal neutron counting are described and compared with each other. The achieved short-term relative precision with both methods is determined by modeling the luminosity curve. It is shown that using cluster counting a short-term relative precision of < 0.5 % can be achieved for 60 s time intervals. For thermal neutrons, a short-term relative precision (for 60 s intervals) of ≈ 2 % was found. Hereby statistics was the limiting factor. The findings are discussed in view of Timepix3 upgrade plans for LHC Run-3.