Relative luminosity measurement of the LHC with the ATLAS forward calorimeter

TL;DR

This paper presents a method to measure relative luminosity at the LHC by analyzing high voltage currents in the ATLAS forward calorimeter, validated through test beam experiments with proton beams.

Contribution

The paper introduces a novel technique for luminosity measurement using calorimeter HV currents, verified with controlled test beam data and showing high linearity and low non-linearity.

Findings

High voltage currents correlate linearly with beam intensity.

Non-linearities are less than 0.5%.

Method validated with test beam data.

Abstract

In this paper it is shown that a measurement of the relative luminosity changes at the LHC may be obtained by analysing the currents drawn from the high voltage power supplies of the electromagnetic section of the forward calorimeter of the ATLAS detector. The method was verified with a reproduction of a small section of the ATLAS forward calorimeter using proton beams of known beam energies and variable intensities at the U-70 accelerator at IHEP in Protvino, Russia. The experimental setup and the data taking during a test beam run in April 2008 are described in detail. A comparison of the measured high voltage currents with reference measurements from beam intensity monitors shows a linear dependence on the beam intensity. The non-linearities are measured to be less than 0.5 % combining statistical and systematic uncertainties.