654 research outputs found
Development of a timing chip prototype in 110 nm CMOS technology
We present a readout chip prototype for future pixel detectors with timing
capabilities. The prototype is intended for characterizing 4D pixel arrays with
a pixel size of , where the sensors are Low Gain
Avalanche Diodes (LGADs). The long-term focus is towards a possible replacement
of disks in the extended forward pixel system (TEPX) of the CMS experiment
during the High Luminosity LHC (HL-LHC). The requirements for this ASIC are the
incorporation of a Time to Digital Converter (TDC) within each pixel, low power
consumption, and radiation tolerance up to
to withstand the radiation levels
in the innermost detector modules for of the HL-LHC (in
the TEPX). A prototype has been designed and produced in 110~nm CMOS technology
at LFoundry and UMC with different versions of TDC structures, together with a
front end circuitry to interface with the sensors. The design of the TDC will
be discussed, with the test set-up for the measurements, and the first results
comparing the performance of the different structures
Characterization of timing and spacial resolution of novel TI-LGAD structures before and after irradiation
The characterization of spacial and timing resolution of the novel Trench Isolated LGAD (TI-LGAD) technology is presented. This technology has been developed at FBK with the goal of achieving 4D pixels, where an accurate position resolution is combined in a single device with the precise timing determination for Minimum Ionizing Particles (MIPs). In the TI-LGAD technology, the pixelated LGAD pads are separated by physical trenches etched in the silicon. This technology can reduce the interpixel dead area, mitigating the fill factor problem. The TI-RD50 production studied in this work is the first one of pixelated TI-LGADs. The characterization was performed using a scanning TCT setup with an infrared laser and a Sr source setup
Characterization of timing and spacial resolution of novel TI-LGAD structures before and after irradiation
The characterization of spacial and timing resolution of the novel Trench
Isolated LGAD (TI-LGAD) technology is presented. This technology has been
developed at FBK with the goal of achieving 4D pixels, where an accurate
position resolution is combined in a single device with the precise timing
determination for Minimum Ionizing Particles (MIPs). In the TI-LGAD technology,
the pixelated LGAD pads are separated by physical trenches etched in the
silicon. This technology can reduce the interpixel dead area, mitigating the
fill factor problem. The TI-RD50 production studied in this work is the first
one of pixelated TI-LGADs. The characterization was performed using a scanning
TCT setup with an infrared laser and a Sr source setup
Search for Flavor-Changing Neutral Current Interactions of the Top Quark and Higgs Boson in Final States with Two Photons in Proton-Proton Collisions at =13 TeV
Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137  fb−1. No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t→Hu) and 0.073% (0.051%) for B(t→Hc). These are the strictest upper limits yet determined
Measurement of the inclusive tt production cross section in proton-proton collisions at = 5.02 TeV
The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb−1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8+2.9−3.1 pb
Fragmentation of jets containing a prompt meson in PbPb and pp collisions at = 5.02 TeV
Jets containing a prompt meson are studied in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using the CMS detector at the LHC. Jets are selected to be in the transverse momentum range of . The yield in these jets is evaluated as a function of the jet fragmentation variable z, the ratio of the to the jet . The nuclear modification factor, , is then derived by comparing the yield in lead-lead collisions to the corresponding expectation based on proton-proton data, at the same nucleon-nucleon center-of-mass energy. The suppression of the yield shows a dependence on z, indicating that the interaction of the with the quark-gluon plasma formed in heavy ion collisions depends on the fragmentation that gives rise to the meson
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