@phdthesis{Karacheban2017, author = {Karacheban, Olena}, title = {Luminosity measurement at CMS}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-43243}, school = {BTU Cottbus - Senftenberg}, year = {2017}, abstract = {Luminosity is a key quantity of any collider, since it allows for the determination of the absolute cross sections from the observed rates in a detector. Since the Higgs boson discovery in 2012, the highest priority at the Large Hadron Collider (LHC) has been given to an accurate understanding of the electroweak scale and a search for new physics. Precise luminosity measurements in such conditions are of crucial importance, as they determine the precision of any physics cross section measurement. To increase the production of particles of low cross section the LHC is running at the highest possible luminosity. After the first Long Shutdown (LS1) the original performance goal for the luminosity of was reached with 1011 protons per bunch and a bunch spacing of 25 ns. In such conditions radiation hard detectors with extremely fast response time are required, especially for instrumentation near the beam. The Compact Muon Solenoid experiment is equipped with three online luminometers, which fulfill the listed requirements: the Fast Beam Conditions Monitor (BCM1F), the Pixel Luminosity Telescope (PLT) and the Forward Hadron calorimeter (HF). The BCM1F was upgraded during LS1 from 8 to 24 diamond sensors and is read out by a dedicated fast ASIC. The back-end comprises a deadtime-less histogramming unit, with 6.25 ns bin width and analog-to-digital converters with 2 ns sampling time in the VME standard. A microTCA system with better time resolution is in development. Because of its excellent time resolution BCM1F measures separately both luminosity and machine induced background particles. The performance of the detector in the first running period and radiation damage monitoring of the sensors and electronics chain form the first part of this thesis. Calibration of the luminometers at the LHC is done using van der Meer (VdM) scans. The proton beams are scanned against each other. The effective width of the beams is measured and the visible cross section, the key quantity for the luminosity measurement, is determined. The impact of detector instability, beam-beam effects, correlations of the particle density distributions in the X and Y planes, and satellite and ghost bunches are studied in detail and systematic uncertainties are derived. A comparison of the VdM scans of 2015 and 2016 completes the second part of the thesis. As a contribution to the upgrade of the beam instrumentation for the high luminosity LHC, a novel single crystal sapphire detector was designed, built and studied in a test-beam. The detector comprises a stack of sapphire plates. The response depends on the direction of the incident particles. The performance of the detector is described in the third part of the thesis. It is demonstrated that this sapphire detector can be used for the detection of single relativistic particles. The results point to the dominant contribution of the electrons to the signal generation in sapphire.}, subject = {Collider; Luminosity; Diamond sensors; Van der Meer scan; Sapphire sensors; Collider; Luminosit{\"a}t; Diamant-Sensoren; Van der Meer Scan; Saphir-Sensoren; LHC; Lumineszenz; Sensor; Saphir}, language = {en} }