Luminosity Measurement at the Compact Linear Collider

The compact linear collider (CLIC) is a proposed high energy accelera- tor, planned to collide electrons with positrons at a maximal center-of-mass energy of 3 TeV, and a peak luminosity of 5.9·1034 cm−2s−1. Complementary to the large hadron collider, CLIC is to provide high precision measurements of both known and new physics processes. The required relative precision of luminosity measurement at the CLIC is 10−2. The measurement will be done by the luminosity calorimeter (Lumi- Cal), designed to measure the rate of low angles Bhabha scattering events, a process with well-known cross-section from electroweak theory. Beam-beam effects, which are of unprecedented intensity at the CLIC, influence the lumi- nosity spectrum shape and create a significant amount of background charge deposits in the LumiCal, thus setting a challenge on the requirement for precision. The ability of the LumiCal to provide accurate luminosity mea- surement depends on its ability to perform accurate energy reconstruction of Bhabha events. In this work, the issue of in-situ calibration of the LumiCal is addressed for the first time. Using a wide range of software tools, the foreseen luminosity spectrum is fully simulated and reconstructed, and a process of calibration is established and proven to be feasible with adequate accuracy. In addition, the issue of energy resolution of the LumiCal is re-examined within the full detector simulation, and in the presence of beam-induced background, with implications on time-stamping of the readout electronics.