Preparing Electrons and Photons High Level Trigger Reconstruction in CMS for Run II data taking

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Beurs van Berlage

Beurs van Berlage

Poster Data-processing: 3b) Trigger and Data Acquisition Systems


Simon Regnard (Ecole Polytechnique (FR))


The CMS experiment has been designed with a 2-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 algorithm. New approaches have been studied to keep the HLT output rate manageable while maintaining thresholds low enough to cover physics analyses. The strategy mainly relies on porting online the ingredients that have been successfully applied in the offline reconstruction, thus allowing to move HLT selection closer to offline cuts. We will present such improvements in the definitions of HLT electrons and photons, focusing in particular on the deployment of a new superclustering algorithm allowing pileup mitigation, a new Particle-Flow-based isolation replacing the less powerful detector-based approach, and an electron-dedicated track fitting algorithm based on a Gaussian Sum Filter.

Primary author

Matteo Sani (Univ. of California San Diego (US))


Simon Regnard (Ecole Polytechnique (FR))

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