Abstract

A network of 16 Medipix-2 (MPX) silicon pixel devices was installed in the ATLAS detector cavern at CERN. It was designed to measure the composition and spectral characteristics of the radiation field in the ATLAS experiment and its surroundings. This study demonstrates that the MPX network can also be used as a self-sufficient luminosity monitoring system. The MPX detectors collect data independently of the ATLAS data-recording chain, and thus they provide independent measurements of the bunch-integrated ATLAS/LHC luminosity. In particular, the MPX detectors located close enough to the primary interaction point are used to perform van der Meer calibration scans with high precision. Results from the luminosity monitoring are presented for 2012 data taken at sqrt(s) = 8 TeV proton-proton collisions. The characteristics of the LHC luminosity reduction rate are studied and the effects of beam-beam (burn-off) and beam-gas (single bunch) interactions are evaluated. The systematic variations observed in the MPX luminosity measurements are below 0.3% for one minute intervals.

Highlights

  • A comprehensive analysis of data taken by a network of Medipix-2 (MPX) devices as a self-sufficient luminosity monitoring system is presented

  • The MPX devices are based on the Medipix2 hybrid silicon pixel detector which was developed by the Medipix-2 Collaboration [2]

  • This study has demonstrated that the MPX network is well suited for luminosity monitoring

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Summary

INTRODUCTION

A comprehensive analysis of data taken by a network of Medipix-2 (MPX) devices as a self-sufficient luminosity monitoring system is presented. The MPX devices are based on the Medipix hybrid silicon pixel detector which was developed by the Medipix-2 Collaboration [2]. The methods and techniques described in this article were pioneered for high-precision luminosity determination for the 2012 data-taking period at the LHC. These techniques and analysis methods are based on precision counting of particles passing the sensors.

MPX LUMINOSITY FROM HIT COUNTING
RELATION BETWEEN HITS AND CLUSTERS
VAN DER MEER SCANS
LHC LUMINOSITY CURVE AND MPX SHORT-TERM PRECISION
35 LHC fill 3236
Findings
CONCLUSIONS
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