Bonn 2020 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 20: Instrumentation III

HK 20.6: Talk

Tuesday, March 31, 2020, 18:15–18:30, J-HS C

Event reconstruction for dark photon searches at the NA64 experiment at CERN — •Srijan Sehgal, Nabeel Ahmed, Michael Hösgen, and Bernhard Ketzer — Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany

The NA64 experiment is an active beam-dump experiment at CERN, searching for possible vector particles as a portal to a hypothetical dark matter sector. High-energy beam electrons are tracked and then stopped in a hermetic calorimeter, which acts as an active target. Interesting events are those, where not the full energy has been deposited in the calorimeter.

The presentation describes the event reconstruction for the 2017 and 2018 data for the invisible mode. In this mode some energy is lost by producing a dark photon, which then flies through the detector without interacting. For the alignment of the tracking detectors, we use the principle of least-squares minimization that takes into account both global (e.g. positional correction) and local (e.g. slope of track) parameters. The talk will also cover the Monte-Carlo reconstruction of particle tracks and the energy deposited in the calorimeter for the 2018 visible mode data. In the visible mode the dark photon is produced in an additionally placed tungsten calorimeter and decays into an e⁻e⁺ pair, which is detected by the downstream detectors.

These studies advance the implementation of the data analysis in the CORAL and PHAST frameworks, providing a more flexible and more modular environment than the monolithic code presently used by the NA64 collaboration.