Münster 2017 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 17: HK+T Joint Session III: Gas Detectors/GEM
HK 17.1: Talk
Tuesday, March 28, 2017, 11:00–11:15, F 102
The tracking system for NA64 at CERN SPS — •Michael Hösgen, NA64 Collaboration, and Bernhard Ketzer — Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Deutschland
NA64 is a new experiment at CERN SPS, which conducts a direct search for invisible decays of sub-GeV dark photons (A′). The A′ might be produced by 100 GeV electrons incident on an active target Electromagnetic Calorimeter (ECAL) in the reaction e−Z→ e−ZA′ via kinetic mixing with photons. The A’s supposedly decay invisibly into dark matter particles resulting in a large amount of missing energy.
To verify the momentum of the incident electrons and to clean-up the event sample, tracking of the electrons is crucial for this experiment. The tracking system utilises four Micromegas (MM) and two Gas Electron Multiplier (GEM) detectors. The GEM detectors used in the tracking system have three 10×10 (cm)2 standard GEM foils and a two layer strip readout resulting in 256 channels per plane. As conversion gas an Ar/CO2 (70/30) mixture is used. Tracks will be reconstructed using the tracking framework GENFIT II.
In this talk the performance of the tracking system, especially the GEMs, will be presented. I will also show new limits on the γ−A′ mixing deduced from a first run in 2016.