University of Sofia, Faculty of Physics, Atomic Physics Department, 5, James Bourchier Boulevard, BG-1164 Sofia, Bulgaria Ghent University, Department of Physics and Astronomy, Proeftuinstraat 86, BE-9000 Ghent, Belgium Bulgarian Academy of Sciences, Inst. for Nucl. Res. and Nucl. Energy, Tzarigradsko shaussee Boulevard 72, BG-1784 Sofia, Bulgaria Peking University, Department of Technical Physics, CN-100 871 Beijing, China Universidad de Los Andes, Apartado Aereo 4976, Carrera 1E, no. 18A 10, CO-Bogota, Colombia Academy of Scientific Research and Technology of the Arab Republic of Egypt, 101 Sharia Kasr El-Ain, Cairo, Egypt Panjab University, Department of Physics, Chandigarh Mandir 160 014, India Universita e INFN, Sezione di Bari, Via Orabona 4, IT-70126 Bari, Italy INFN, Laboratori Nazionali di Frascati, PO Box 13, Via Enrico Fermi 40, IT-00044 Frascati, Italy Universita e INFN, Sezione di Napoli, Complesso Univ. Monte S. Angelo, Via Cintia, IT-80126 Napoli, Italy Universita e INFN, Sezione di Pavia, Via Bassi 6, IT-Pavia, Italy Department of Physics and Korea Detector Laboratory, Korea University, Aman-dong 5-ga, Sungbuk-gu, Seou,l Republic of Korea Sungkyunkwan University, Department of Physics 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi-Do, Republic of Korea
The LHC is undergoing a high luminosity upgrade, which is set to increase the instantaneous luminosity by at least a factor of five, resulting in a higher muon flux rate in the forward region, which will overwhelm the current trigger system of the CMS experiment. The ME0, a gas electron multiplier detector, is proposed for the Phase-2 Muon System Upgrade to help increase the muon acceptance and to control the Level 1 muon trigger rate. To lower the probability of HV discharges, the ME0 was designed with GEM foils that are segmented on both sides. Initial testing of the ME0 showed substantial crosstalk between readout sectors. Here, we investigate, characterize, and quantify the crosstalk in the detector, and estimate the performance of the chamber as a result of this crosstalk via simulation of the detector dead time, efficiency loss, and frontend electronics response. The results of crosstalk via signals produced by applying a square voltage pulse directly on the readout strips of the detector with a pulser are summarized, and the efficacy of various mitigation strategies are presented. The crosstalk is a result of capacitive coupling between the readout strips on the readout board and between the readout strips and the bottom of GEM3. The crosstalk also generally follows a pattern where the largest magnitude of crosstalk is within the same azimuthal readout segment in the detector and in the nearest horizontal segments. The use of bypass capacitors and larger HV segments successfully reduce the crosstalk: we observe a maximum decrease of crosstalk in sectors previously experiencing crosstalk from $(1.66pm0.03)%$ to $(1.11pm0.02)%$ with all HV segments connected in parallel on the bottom of GEM3, with an HV low-pass filter, and an HV divider. These mitigation strategies slightly increase crosstalk $big(hspace{-0.1cm}lessapprox 0.4%big)$ in readout sectors farther away.
A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95pm0.05,%$, while the intrinsic spatial resolutions are $4.80pm0.25,mu mathrm{m}$ and $7.99pm0.21,mu mathrm{m}$ along the $100,mu mathrm{m}$ and $150,mu mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.