Vorschau

PDF, Englisch Download (27MB) | Nutzungsbedingungen

Abstract

ATLAS is one of the four big experiments at the Large Hadron Collider (LHC). In order to accurately measure cross sections, the precise knowledge of the integrated luminosity is a prerequisite. The relative luminosity is measured with various detectors and algorithms. The purpose of the algorithms is to convert raw rates measured by a detector into a quantity which is proportional to the luminosity. In this work, three algorithms linked to the two main ATLAS luminosity detectors are absolutely calibrated: BCMH_EventOR, BCMV_EventOR, and LUCID_EventOR. The determination of the calibration constants is based on Van der Meer (VdM) scans, which were carried out in July and November 2012. The statistical errors of this method are negligible and the precision is limited by systematic uncertainties. The different uncertainty sources are quantitatively estimated. The overall uncertainty on the calibration constants is estimated to be 5.40% for the July VdM scans and 2.50% for the November VdM scans. The November calibration is used to determine the integrated luminosity in 2012, its overall uncertainty is evaluated to be 3.30%. The preliminary official ATLAS luminosity and its uncertainty for proton-proton collisions at √s = 8 TeV in the year 2012 are based on this work.