The CMS Level-1 Trigger for LHC Run II

During LHC Run II the centre-of-mass energy of pp collisions has increased up to 13 TeV and the instantaneous luminosity has progressed towards 2×10^34 cm^−2 s^−1. In order to guarantee a successful and ambitious physics programme under these conditions, the CMS trigger system system has been upgraded. The upgraded CMS Level-1 trigger is designed to improve performance at high luminosity and large number of simultaneous inelastic collisions per crossing. The trigger design, implementation and commissioning are summarised and early performance results are described.