Ponente
Hwi Dong Yoo
Descripción
During the first three years of data taking at the LHC, considerable advances in understanding and controlling systematic effects in luminosity determination were made both by the experiments and by the accelerator. The precision achieved with the CMS experiment is 2.6% for the pp data taking in 2012 at 8 TeV. This is an unprecedented precision at a hadron collider, comparable in size with the systematic uncertainty with which the inclusive W and Z cross sections are measured with CMS. The absolute luminosity calibration is obtained from dedicated Van der Meer scans performed by the LHC. Several detectors and algorithms, among them the Hadron Forward calorimeters and the pixel cluster counting algorithm are used in CMS as luminometers. In this talk, the performance of the CMS luminometers, their stability and consistency will be described. The Van der Meer methodology for absolute luminosity calibration will be discussed. An alternative method of luminosity calibration that does not require dedicated LHC runs is the analysis of standard candle processes. Z production is one such processes. The production rate of Z bosons, measured in the dimuon decay, is used. The performance will be compared to the other available methods. Luminosity results will be given for proton-proton running at 2.76 TeV and at 8 TeV, as well as for proton-lead-ion running. Upgrades to the luminosity system for the LHC run starting in 2015 include the addition of two new luminometers. One is the Fast Beam Conditions Monitor, a diamond sensor system, the other the Pixel Luminosity Telescope. The expected benefits for luminosity monitoring and calibration from these upgrades will also be covered.
Autor primario
Arnd Meyer
(RWTH Aachen University)
