No Arabic abstract
The design, construction and test of a charged particle detector made of scintillation counters read by Silicon Photomultipliers (SiPM) is described. The detector, which operates in vacuum and is used as a veto counter in the NA62 experiment at CERN, has a single channel time resolution of 1.14 ns, a spatial resolution of ~2.5 mm and an efficiency very close to 1 for penetrating charged particles.
The NA62 experiment is a fixed-target experiment at CERN SPS. The main goal of the experiment is to measure the branching ratio of the ultra-rare kaon decay $K^{+}topi^{+} ubar u$. The NA62 detector allows also to study other rare kaon decays and to search for very weakly coupled particles of MeV-GeV mass-scale. The new ANTI-0 hodoscope is proposed and designed to veto events with charged halo particles entering the decay volume. It is now being assembled at CERN. The detector design, the performance simulation and the results of measurements with cosmic rays and test beams for the individual elements are presented. The commissioning and the first run of data-taking is scheduled for after the end of LS2 long shutdown (April 2021).
The branching ratio (BR) for the decay K^+ rightarrow pi^+ u bar{ u} 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 dominant background from channels with final state photons, the large-angle vetoes (LAVs) must detect photons of energy as low as 200 MeV with an inefficiency of less than 10^-4, as well as provide energy and time measurements with resolutions of 10% and 1 ns for 1 GeV photons. The LAV detectors make creative reuse 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.
The NA61 Experiment at CERN SPS is a large acceptance hadron spectrometer, aimed to studying of hadron-hadron, hadron-nucleus, and nucleus-nucleus interactions in a fixed target environment. The present paper discusses the construction and performance of the Low Momentum Particle Detector (LMPD), a small time projection chamber unit which has been added to the NA61 setup in 2012. The LMPD considerably extends the detector acceptance towards the backward region, surrounding the target in hadron-nucleus interactions. The LMPD features simultaneous range and ionization measurements, which allows for particle identification and momentum measurement in the 0.1-0.25 GeV/c momentum range for protons. The possibility of Z=1 particle identification in this range is directly demonstrated.
The Ring Imaging Cherenkov detector is crucial for the identification of charged particles in the NA62 experiment at the CERN SPS. The detector commissioning was completed in 2016 by the precise alignment of mirrors using reconstructed tracks. The alignment procedure and measurement of the basic performance are described. Ring radius resolution, ring centre resolution, single hit resolution and mean number of hits per ring are evaluated for positron tracks. The contribution of the residual mirror misalignment to the performance is calculated.
The NA62 experiment at CERN aims to make a precision measurement of the ultra-rare decay $K^{+} rightarrow pi^{+} uoverline{ u}$, and relies on a differential Cherenkov detector (KTAG) to identify charged kaons at an average rate of 50 MHz in a 750 MHz unseparated hadron beam. The experimental sensitivity of NA62 to K-decay branching ratios (BR) of $10^{-11}$ requires a time resolution for the KTAG of better than 100 ps, an efficiency better than 95% and a contamination of the kaon sample that is smaller than $10^{-4}$. A prototype version of the detector was tested in 2012, during the first NA62 technical run, in which the required resolution of 100 ps was achieved and the necessary functionality of the light collection system and electronics was demonstrated.