Electron and Photon High Level Trigger in CMS for Run II

The CMS experiment has been designed with a two-level trigger system. The first level is implemented on custom-designed electronics. The second level is the so-called High Level Trigger (HLT), a streamlined version of the CMS offline reconstruction software running on a computer farm. For Run II of the Large Hadron Collider, the increase in center-of-mass energy and luminosity will raise the event rate to a level challenging for the HLT algorithms. New approaches have been studied to contain the HLT rate within the available bandwidth while keeping thresholds low enough to cover the requirements of the physics analyses. The strategy mainly relies on porting online the improvements that have been applied to the offline reconstruction, thus allowing to move HLT selection closer to offline cuts. We present such changes in the definitions of HLT electrons and photons, focusing in particular on the deployment of a new clustering algorithm allowing pileup mitigation, a new Particle-Flow based isolation replacing the detector based method used in Run I, and an electron-dedicated track fitting algorithm based on a Gaussian Sum Filter.