For the upgrade of the innermost station of the forward muon spectrometer of the ATLAS experiment large Micromegas (MM) detectors of 2 and 3 m2 with 4 active layers each are foreseen. Four types of ...MM chambers are produced among four sites. Each sites has to deliver 32 quadruplets or 128 active planes. The tiny 120μm distance between the 600 V resistive strip anodes and the ground micro-meshes for these large areas require adequate and well adapted cleaning procedures to guarantee high voltage stability. This is particularly critical for strip shaped surfaces made from resistive material where remnants from the lithographic production processes must be completely removed. The procedure foreseen a visual inspections to be carried on during cleaning and assembly procedures; a wet cleaning procedure to remove dust and possible ionic components of salts from the anode surfaces; a dry cleaning procedure to remove dust; HV tests to be done to validate the cleaning. The cleaning procedure will be illustrated for a New Small Wheel (NSW) Outer Small Module (SM2) of 2 m2.
A precision measurement of the ratio RK of the rates of kaon leptonic decays K±→e±ν and K±→μ±ν with the full data sample collected by the NA62 experiment at CERN in 2007–2008 is reported. The result, ...obtained by analysing ∼150000 reconstructed K±→e±ν candidates with 11% background contamination, is RK=(2.488±0.010)×10−5, in agreement with the Standard Model expectation.
The branching ratio (BR) for the decay K+ → π+ν is a sensitive probe for new physics. The NA62 experiment at the CERN SPS will measure this BR to within about 10 . To reject the background from ...dominant kaon decays with final state photons, the large-angle photon vetoes (LAVs) must detect photons of energy as low as 200 MeV with an inefficiency of less than 10−4. The LAV detectors make use of lead glass blocks recycled from the OPAL electromagnetic calorimeter barrel. We describe the mechanical design and challenges faced during construction, the characterization of the lead glass blocks and solutions adopted for monitoring their performance, and the development of front-end electronics to allow simultaneous time and energy measurements over an extended dynamic range using the time-over-threshold technique. Our results are based on test-beam data and are reproduced by a detailed Monte Carlo simulation that includes the readout chain.
We have measured the cross section σ(e+e−→π+π−γ(γ)) at DAΦNE, the Frascati ϕ-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. ...We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb−1. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<Mππ<0.975 GeV. For the latter we find Δππaμ=(387.2±0.5stat±2.4exp±2.3th)×10−10.
Large-size Resistive Micromegas have been chosen for the upgrade of the forward muon spectrometer of the ATLAS experiment, the New Small Wheel project. These chambers, together with small-strip Thin ...Gap Chambers (sTGC), allow reconstruction of high-momentum muon tracks in a high-radiation environment and provide a robust low-threshold single-muon trigger. A collaboration of seven INFN units built 32 SM1 type chambers, corresponding to one fourth of the total number needed for this upgrade. Each SM1 chamber has a surface of approximately 2 m2 and four sensitive layers. The production was shared among five INFN construction sites and it was completed in fall 2020. The construction methods, as well as the results of the quality tests done on components of the detector and on the assembled chambers, are reported in the present paper.
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