We present a new measurement of the positive muon magnetic anomaly, a µ ≡ (gµ − 2)/2, from the Fermilab Muon g −2 Experiment based on data collected in 2019 and 2020. We have analyzed more than four times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of two due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω′ p , and of the anomalous precession frequency corrected for beam dynamics effects, ωa. From the ratio ωa/ω ′ p , together with precisely determined external parameters, we determine a µ = 116 592 057(25) × 10 −11 (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain a µ (FNAL) = 116 592 055(24) × 10 −11 (0.20 ppm). The new experimental world average is aµ(Exp) = 116 592 059(22) × 10 −11 (0.19 ppm), which represents a factor of two improvement in precision.
We present the FP420 R&D project, which has been studying
the key aspects of the development and installation of a silicon
tracker and fast-timing detectors in the LHC tunnel at 420 m from
the interaction points of the ATLAS and CMS experiments. These
detectors would measure precisely very forward protons in
conjunction with the corresponding central detectors as a means to
study Standard Model (SM) physics, and to search for and
characterise new physics signals. This report includes a detailed
description of the physics case for the detector and, in particular,
for the measurement of Central Exclusive Production, pp→p+ϕ+p, in which the outgoing protons remain intact and the
central system ϕ may be a single particle such as a SM or MSSM
Higgs boson. Other physics topics discussed are γγ and
γp interactions, and diffractive processes. The report
includes a detailed study of the trigger strategy, acceptance,
reconstruction efficiencies, and expected yields for a particular
pp→pHp measurement with Higgs boson decay in the
bb̄ mode. The document also describes the detector
acceptance as given by the LHC beam optics between the interaction
points and the FP420 location, the machine backgrounds, the new
proposed connection cryostat and the moving (``Hamburg'') beam-pipe
at 420 m, and the radio-frequency impact of the design on the
LHC. The last part of the document is devoted to a description of
the 3D silicon sensors and associated tracking performances, the
design of two fast-timing detectors capable of accurate vertex
reconstruction for background rejection at high-luminosities, and
the detector alignment and calibration strategy.
This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully-assembled barrels that make up the detector being installed in the ATLAS experiment.
Charge collection properties of particle detectors made in HV-CMOS technology were investigated before and after irradiation with reactor neutrons. Two different sensor types were designed and processed in 180 and 350 nm technology by AMS. Edge-TCT and charge collection measurements with electrons from 90 Sr source were employed. Diffusion of generated carriers from undepleted substrate contributes significantly to the charge collection before irradiation, while after irradiation the drift contribution prevails as shown by charge measurements at different shaping times. The depleted region at a given bias voltage was found to grow with irradiation in the fluence range of interest for strip detectors at the HL-LHC. This leads to large gains in the measured charge with respect to the one before irradiation. The increase of the depleted region was attributed to removal of effective acceptors removal. The evolution of depleted region with fluence was investigated and modeled. Initial studies show a small effect of short term annealing on charge collection.
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