MPX Detectors as LHC Luminosity Monitor

TL;DR

This paper demonstrates that MPX silicon pixel detectors, installed in the ATLAS detector cavern, can independently measure LHC luminosity with high precision, providing a reliable alternative to traditional methods.

Contribution

The study introduces the use of MPX detectors as a self-sufficient luminosity monitor, capable of independent and precise measurements during LHC operations.

Findings

MPX detectors can measure luminosity independently of the ATLAS data chain.

The systematic variation in MPX luminosity measurements is below 0.3% per minute.

MPX detectors successfully performed van der Meer calibration scans at 8 TeV.

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.