The NA48/2 experiment at CERN reports the first observation of the K±→π±π0e+e− decay from an exposure of 1.7×1011 charged kaon decays recorded in 2003–2004. A sample of 4919 candidates with 4.9% ...background contamination allows the determination of the branching ratio in the full kinematic region, BR(K±→π±π0e+e−)=(4.24±0.14)×10−6. The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on chiral perturbation theory. Several P- and CP-violating asymmetries are also evaluated.
The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the π0 electromagnetic transition form factor ...slope parameter from 1.11×106 fully reconstructed K±→π±πD0, πD0→e+e−γ events is reported. The measured value a=(3.68±0.57)×10−2 is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.
This review summarizes the kaon experimental results obtained in the last 15 years on the basis of data collected on the SPS in CERN with a participance of JINR physicists. These results contribute ...essentially into the Standard Model checks and search for its extension, fundamental symmetry violations and low energy strong interactions theory development. A progress in the experimental technique and prospects for the future results are also discussed.
The Gigatracker (GTK) is a hybrid silicon pixel detector designed for the NA62 experiment at CERN. The beam spectrometer, made of three GTK stations, has to sustain high and non-uniform particle rate ...(∼1GHz in total) and measure momentum and angles of each beam track with a combined time resolution of 150ps. In order to reduce multiple scattering and hadronic interactions of beam particles, the material budget of a single GTK station has been fixed to 0.5% X0. The expected fluence for 100 days of running is 2×1014 1MeVneq/cm2, comparable to the one foreseen in the inner trackers of LHC detectors during 10 years of operation. To comply with these requirements, an efficient and very low-mass (<0.15%X0) cooling system is being constructed, using a novel microchannel cooling silicon plate. Two complementary read-out architectures have been produced as small-scale prototypes: one is based on a Time-over-Threshold circuit followed by a TDC shared by a group of pixels, while the other makes use of a constant-fraction discriminator followed by an on-pixel TDC. The read-out ASICs are produced in 130nm IBM CMOS technology and will be thinned down to 100μm or less. An overview of the Gigatracker detector system will be presented. Experimental results from laboratory and beam tests of prototype bump-bonded assemblies will be described as well. These results show a time resolution of about 170ps for single hits from minimum ionizing particles, using 200μm thick silicon sensors.
The NA62 experiment 1 at the CERN SPS (Super Proton Synchrotron) accelerator studies the ultra-rare decays of charged kaons. The high-resolution Liquid Krypton (LKr) electromagnetic calorimeter of ...the former NA48 experiment 2 is a key component of the experiment photon-veto system. The new LKr readout system comprises 14,000 14-bit ADC acquisition channels, 432x 1 Gbit Ethernet data request and readout links routed by 28x 10 Gbit network switches to the experiment computer farm, and timing, trigger and control (TTC) distribution system. This paper presents the architecture of the LKr readout and TTC systems, the overall performance and the first successfully collected experiment physics data.
The NA62 experiment 1 at CERN SPS (Super Proton Synchrotron) accelerator aims at studying Kaon decays with high precision. The high resolution Liquid Krypton (LKr) calorimeter, built for the NA48 2 ...experiment, is a crucial part of the experiment photon-veto system; to cope with the new requirements, the back-end electronics of the LKr had to be completely renewed. Due to the huge number of the calorimeter readout channels (~ 14 K) and the maintenance requirement over 10 years of the experiment lifetime, the decision to sub-contract the development and production to industry was taken in 2011. This paper presents the primary test results of the Calorimeter REAdout Module (CREAM) 3 prototype delivered by the manufacturer in March 2013. All essential features, analog performance, data processing and readout, are covered.
A sample of 1.69×107 fully reconstructed π0→γe+e− decay candidates collected by the NA48/2 experiment at CERN in 2003–2004 is analyzed to search for the dark photon (A′) production in the π0→γA′ ...decay followed by the prompt A′→e+e− decay. No signal is observed, and an exclusion region in the plane of the dark photon mass mA′ and mixing parameter ε2 is established. The obtained upper limits on ε2 are more stringent than the previous limits in the mass range 9 MeV/c2<mA′<70 MeV/c2. The NA48/2 sensitivity to the dark photon production in the K±→π±A′ decay is also evaluated.
The NA62 experiment 1 at CERN SPS (Super Proton Synchrotron) accelerator will be focused on precision tests of the Standard Model via studies of ultra-rare decays of charged kaons. The high ...resolution Liquid Krypton (LKr) calorimeter of the former NA48 experiment 2, together with other detectors, will provide a photon-veto with hermetic coverage from zero out to large angles from the decay region. The old backend electronics 3 does not satisfy the NA62 specifications and the study of a new readout system began in 2008. This paper presents the Calorimeter REAdout Module (CREAM), an upgrade project for the backend part of the LKr data acquisition chain 3. The CREAMs will provide 40 MHz sampling of 13248 calorimeter channels, data buffering during the SPS spill, zero suppression, and programmable trigger sums for the experiment trigger processor.
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