Performance and upgrade of the CMS electron and photon trigger for Run 2

The CMS experiment implements a sophisticated two-level online trigger selection system that achieves a rejection factor of nearly 10⁵. The first level (L1) trigger is based on coarse information coming from the calorimeters and the muon detectors while the high-level trigger combines fine-grain information from all sub-detectors. In the near future the LHC will increase its centre of mass energy to 13 TeV and progressively reach an instantaneous luminosity of 2 × 10³⁴ cm^-2s^-1. In order to guarantee a successful and ambitious physics program under this challenging environment, the CMS trigger and data acquisition system must be consolidated. In particular the calorimeter L1 trigger hardware and architecture will be changed. The aim is to maintain the current thresholds and improve performance. This programme will be achieved using the μTCA architecture with fast optical links and latest generation FPGAs. Sophisticated object reconstruction algorithms, as well as online pile-up corrections, are being developed that will make use of these new hardware capabilities. For electron and photon reconstruction and identification, the first version of the new algorithms has been tested against the current algorithms. It shows a reduction of the trigger rate by a factor of two for isolated objects, an improved energy resolution of about 30%, and a position resolution reduced by more than four.