Analysis of the behavior of the poly-crystalline diamond sensors of the BCM1F detector and luminosity measurement at the CMS Experiment

For determination of the cross sections of physical processes, it is essential to measure the luminosity as accurately as possible. This is done by measuring the event rate. From the visible cross section of a so-called luminometer the total luminosity can be extrapolated. The visible cross section is determined in calibration measurements (Van der Meer scans). If the visible cross section is known for a luminometer, the instantaneous luminosity can be measured in real-time. Several luminometers are used in the CMS experiment. One of these detectors is the Fast Beam Condition Monitor (BCM1F). The BCM1F detector is located directly at the beam pipe, on both sides at a distance of 1.8 m from the interaction point. However, the efficiency of these sensors shows a dependency on the absolute event rate. For its calibration the per bunch luminosity changing during a fill of the collider has to be considered. Also the total Luminosity, which for example depends on the number of bunches in a fill, has an influence on the efficiency of the sensors. In the talk the luminosity measurement at the CMS experiment as well as the calibration of BCM1F are presented.