Abstract
A network of Timepix (TPX) devices installed in the ATLAS cavern measures the LHC luminosity as a function of time as a stand-alone system. The data were recorded from 13 TeV proton-proton collisions in 2015. Using two TPX devices, the number of hits created by particles passing the pixel matrices was counted. A van der Meer scan of the LHC beams was analysed using bunch-integrated luminosity averages over the different bunch profiles for an approximate absolute luminosity normalization. It is demonstrated that the TPX network has the capability to measure the reduction of LHC luminosity with precision. Comparative studies were performed among four sensors (two sensors in each TPX device) and the relative short-term precision of the luminosity measurement was determined to be 0.1% for 10 s time intervals. The internal long-term time stability of the measurements was below 0.5% for the data-taking period.
Highlights
A TPX detector network [1] of 16 devices was installed in the ATLAS cavern at CERN
The analysis described in this paper is focused on the precision luminosity determination with the devices TPX02 and TPX12, which are operated with a 1-s exposure time and analyzed in hit counting mode
Further uncertainties could arise from nonGaussian shapes, this paper shows that the Gaussian approximation of the sum of Gaussians is quite robust with the TPX system and the luminosity approximation by bunch integration is a sensible approach
Summary
A TPX detector network [1] of 16 devices was installed in the ATLAS cavern at CERN. Each TPX device consists of two stacked hybrid silicon pixel sensors. The analysis described in this paper is focused on the precision luminosity determination with the devices TPX02 and TPX12, which are operated with a 1-s exposure time and analyzed in hit counting mode. As their positions are very similar in R and Z coordinates on opposite sides of the proton–proton interaction point, their count rates are very similar.
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