Abstract
The CMS GEM collaboration is performing a feasibility study to install triple-GEM detectors in the forward region of the muon system (1.6 < |η| < 2.4) of the CMS detector at the LHC. Such micro-pattern gas detectors are able to cope with the extreme particle rates that are expected in that region during the High Luminosity phase of the LHC. With their spatial resolution of order 100 micron GEMs would not only provide additional benefits in the CMS muon High Level Trigger, but also in the muon identification and track reconstruction, effectively combining tracking and triggering capabilities in one single device. The present status of the full project will be reviewed, highlighting all importants steps and achievements since the start of the R&D in 2009. Several small and full-size prototypes were constructed with different geometries and techniques. The baseline design of the triple-GEM detector for CMS will be described, along with the results from extensive test measurements of all prototypes both in the lab and in test beams at the CERN SPS. The proposed on- and off-detector electronics for the final system will be presented.
Highlights
12 z (m) issue with respect to muon triggering in this region is the high background rate stemming from low-pT tracks that are misidentified as high-pT muons
After over 4 years of R&D, the design and characterization is close to being finalized of tripleGEM chambers suitable for the extension of the CMS Muon System in the forward region
A CMS GEM data-acquisition system based on VFAT3 front-end chips and the GBT-GLIB optical link system is under development
Summary
Issue with respect to muon triggering in this region is the high background rate stemming from low-pT tracks that are misidentified as high-pT muons. Adding more detection layers with high granularity at high |η| will yield additional space points for track reconstruction to be combined with the information from the CSCs. Adding more detection layers with high granularity at high |η| will yield additional space points for track reconstruction to be combined with the information from the CSCs This will improve both the muon momentum resolution and the background rejection at the trigger level, especially in the inner endcap stations where the muon track bending angle due to the magnetic field from the CMS solenoid is largest. The CMS GEM Collaboration aims at installing several layers of triple-GEMs in the 1.5 < |η| < 2.4 region of the Muon System. Pairs of triple-GEM chambers combined together to form super-chambers, would be installed in the two inner endcap stations of the Muon System, as indicated in figure 1. In the presently proposed schedule, the inner endcap stations would be equipped with GEMs (labeled GE1/1) during the second LHC Long Shutdown in 2017–2018, while the installation in the second endcap stations (labeled GE2/1) would be done during the third LHC Long Shutdown scheduled beyond 2020
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