CERN NA62 Research Articles

The NA62 GigaTracKer: a low mass high intensity beam 4D tracker with 65 ps time resolution on tracks

The GigaTracKer (GTK) is the beam spectrometer of the CERN NA62 experiment. The detector features challenging design specifications, in particular a peak particle flux reaching up to 2.0 MHz/mm2, a single hit time resolution smaller than 200 ps and, a material budget of 0.5% X0 per tracking plane. To fulfil these specifications, novel technologies were especially employed in the domain of silicon hybrid time-stamping pixel technology and micro-channel cooling. This article describes the detector design and reports on the achieved performance.

The integrated low-level trigger and readout system of the CERN NA62 experiment

The integrated low-level trigger and data acquisition (TDAQ) system of the NA62 experiment at CERN is described. The requirements of a large and fast data reduction in a high-rate environment for a medium-scale, distributed ensemble of many different sub-detectors led to the concept of a fully digital integrated system with good scaling capabilities. The NA62 TDAQ system is rather unique in allowing full flexibility on this scale, allowing in principle any information available from the detector to be used for triggering. The design concept, implementation and performances from the first years of running are illustrated.

Development of Network Interface Cards for TRIDAQ systems with the NaNet framework

NaNet is a framework for the development of FPGA-based PCI Express (PCIe) Network Interface Cards (NICs) with real-time data transport architecture that can be effectively employed in TRIDAQ systems. Key features of the architecture are the flexibility in the configuration of the number and kind of the I/O channels, the hardware offloading of the network protocol stack, the stream processing capability, and the zero-copy CPU and GPU Remote Direct Memory Access (RDMA). Three NIC designs have been developed with the NaNet framework: NaNet-1 and NaNet-10 for the CERN NA62 low level trigger and NaNet3 for the KM3NeT-IT underwater neutrino telescope DAQ system. We will focus our description on the NaNet-10 design, as it is the most complete of the three in terms of capabilities and integrated IPs of the framework.

Status of the CERN NA62 Experiment

The decay is one of the theoretically cleanest meson decays to look for indirect effects of new physics in a complementary way to direct searches at the LHC. The NA62 experiment at CERN SPS is designed to measure the branching ratio of this decay with 10% precision. NA62 is taking data since 2014, eventually reaching the final designed beam intensity. Using a sample of data taken in 2015, the experimental performances in view of the branching ratio measurement is reported.

Graphical processors for HEP trigger systems

General-purpose computing on GPUs is emerging as a new paradigm in several fields of science, although so far applications have been tailored to employ GPUs as accelerators in offline computations. With the steady decrease of GPU latencies and the increase in link and memory throughputs, time is ripe for real-time applications using GPUs in high-energy physics data acquisition and trigger systems. We will discuss the use of online parallel computing on GPUs for synchronous low level trigger systems, focusing on tests performed on the trigger of the CERN NA62 experiment. Latencies of all components need analysing, networking being the most critical. To keep it under control, we envisioned NaNet, an FPGA-based PCIe Network Interface Card (NIC) enabling GPUDirect connection. Moreover, we discuss how specific trigger algorithms can be parallelised and thus benefit from a GPU implementation, in terms of increased execution speed. Such improvements are particularly relevant for the foreseen LHC luminosity upgrade where highly selective algorithms will be crucial to maintain sustainable trigger rates with very high pileup.

Graphics Processors in HEP Low-Level Trigger Systems

Usage of Graphics Processing Units (GPUs) in the so called general-purpose computing is emerging as an effective approach in several fields of science, although so far applications have been employing GPUs typically for offline computations. Taking into account the steady performance increase of GPU architectures in terms of computing power and I/O capacity, the real-time applications of these devices can thrive in high-energy physics data acquisition and trigger systems. We will examine the use of online parallel computing on GPUs for the synchronous low-level trigger, focusing on tests performed on the trigger system of the CERN NA62 experiment. To successfully integrate GPUs in such an online environment, latencies of all components need analysing, networking being the most critical. To keep it under control, we envisioned NaNet, an FPGA-based PCIe Network Interface Card (NIC) enabling GPUDirect connection. Furthermore, it is assessed how specific trigger algorithms can be parallelized and thus benefit from a GPU implementation, in terms of increased execution speed. Such improvements are particularly relevant for the foreseen Large Hadron Collider (LHC) luminosity upgrade where highly selective algorithms will be essential to maintain sustainable trigger rates with very high pileup.

Graphics Processing Units for HEP trigger systems

General-purpose computing on GPUs (Graphics Processing Units) is emerging as a new paradigm in several fields of science, although so far applications have been tailored to the specific strengths of such devices as accelerator in offline computation. With the steady reduction of GPU latencies, and the increase in link and memory throughput, the use of such devices for real-time applications in high-energy physics data acquisition and trigger systems is becoming ripe. We will discuss the use of online parallel computing on GPU for synchronous low level trigger, focusing on CERN NA62 experiment trigger system. The use of GPU in higher level trigger system is also briefly considered.

The New Readout System of the NA62 LKr Calorimeter

The NA62 experiment 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 experiment, is a crucial part of the photon-veto system; to cope with the demanding NA62 requirements, its back-end electronics had to be completely renewed. The new readout system is based on the Calorimeter REAdout Module (CREAM) , a 6U VME board whose design and production was sub-contracted to CAEN , with CERN NA62 group continuously supervising the development and production phase. The first version of the board was delivered by the manufacturer in March 2013 and, as of June 2014, the full board production is ongoing. In addition to describing the CREAM board, all aspects of the new LKr readout system, including its integration within the NA62 TDAQ scheme, will be treated.

GPUs for real-time processing in HEP trigger systems

We describe a pilot project (GAP – GPU Application Project) for the use of GPUs (Graphics processing units) for online triggering applications in High Energy Physics experiments. Two major trends can be identified in the development of trigger and DAQ systems for particle physics experiments: the massive use of general-purpose commodity systems such as commercial multicore PC farms for data acquisition, and the reduction of trigger levels implemented in hardware, towards a fully software data selection system ("trigger-less"). The innovative approach presented here aims at exploiting the parallel computing power of commercial GPUs to perform fast computations in software not only in high level trigger levels but also in early trigger stages. General-purpose computing on GPUs is emerging as a new paradigm in several fields of science, although so far applications have been tailored to the specific strengths of such devices as accelerators in offline computation. With the steady reduction of GPU latencies, and the increase in link and memory throughputs, the use of such devices for real-time applications in high energy physics data acquisition and trigger systems is becoming relevant. We discuss in detail the use of online parallel computing on GPUs for synchronous low-level triggers with fixed latency. In particular we show preliminary results on a first test in the CERN NA62 experiment. The use of GPUs in high level triggers is also considered, the CERN ATLAS experiment being taken as a case study of possible applications.

The FPGA based Trigger and Data Acquisition system for the CERN NA62 experiment

The main goal of the NA62 experiment at CERN is to measure the branching ratio of the ultra-rare K+→π+νν̄ decay, collecting about 100 events to test the Standard Model of Particle Physics. Readout uniformity of sub-detectors, scalability, efficient online selection and lossless high rate readout are key issues. The TDCB and TEL62 boards are the common blocks of the NA62 TDAQ system. TDCBs measure hit times from sub-detectors, TEL62s process and store them in a buffer, extracting only those requested by the trigger system following the matching of trigger primitives produced inside TEL62s themselves. During the NA62 Technical Run at the end of 2012 the TALK board has been used as prototype version of the L0 Trigger Processor.

The NA62 RICH Detector

Abstract The CERN NA62 experiment aims to measure the ultra-rare charged kaon decay K + → π + νν (branching fraction O(10 -10 )) with a 10% accuracy. The detector must be able to reject background events from decay channels of which the branching fractions are up to 10 orders of magnitude larger than the signal and with similar experimental signature. To totally suppress the main background from K + →μ + ν decay (BR ∼ 63%), NA62 will need a further μ rejection factor better than 5x10 -3 . This will be provided by a gas RICH detector for π/μ separation in a momentum range between 15 and 35 GeV/c. The details of the RICH project will be described and the results of two beam tests performed at CERN with prototypes will be presented.

Lepton flavour universality test at the CERN NA62 experiment

A precision test of lepton universality by measurement of the ratio R K of K + → e + ν to K + → μ + ν decay rates was performed using a sample of 59963 K + → e + ν candidates with 8.8% background contamination collected by the CERN NA62 experiment. The result R K = ( 2.486 ± 0.013 ) × 10 − 5 is in agreement with the Standard Model expectation.

CP violation results on Kaons by the NA48 experiment

Recent results on CP violation on kaons by the CERN NA48 experiment will be discussed. A preliminary measurement of the charge asymmetry in KL → π±e∓ν has been made: δLe = (3.317±0.070stat±0.072syst) × 10−3. A search for KS → 3π0 decays has been performed with a preliminary estimation of the real and imaginary part of the η000 parameter: Re(η000) = (−2.6±1.0stat±0.5syst) × 10−2 and Im(ηn000) = (−3.4±1.0tstat±1.1syst) × 10−2. The angular asymmetry in KL → π+π−e+e− has been measured to be AL = (14.2 ± 3.0stat ± 1.9syst)%, while no asymmetry has been observed in K → π+π−e+e−: AS = (0.5 ± 4.0stat ± 1.6syst)%. Finally, the direct CP violation in KnS,L → 2π has been clearly settled, with tRe(e′/e) = (14.7 ± 2.2) × 10−4.

Formula omitted] results from NA48 and KTeV E832

After more than 25 years of intense experimental effort, the parameter Re( ε′ ε ) which characterizes direct CP violation in the neutral kaon system has been accurately measured by both the Fermilab KTeV E832 and the Cern NA48 experiments. The latest results presented here demonstrate unambiguosly the existence of direct CP violation. The experimental challenge is reviewed, and the techniques used to extract the parameter are discussed. The current situation is given and future propects are briefly sketched.

The CERN NA48 experiment: status and perspectives

The status of the CERN NA48 experiment aimed at measuring the direct CP violation in the K 0 − K − 0 system is presented. The performances of the apparatus are discussed for the 1997 and 1998 data taking periods.

A 40 MHz-pipelined trigger for K0→2π0 decays for the CERN NA48 experiment

The “neutral” trigger system for the selection of K0→2π0→4γ decays of the NA48 CP-violation experiment is described. The trigger system has been implemented in a 40MHz “dead-time free” pipeline to allow large rate reduction and high-trigger efficiency. The trigger decision is based on the information from 13340cells of the electro-magnetic calorimeter. Every 25ns the energy, the centre of gravity, the kaon lifetime and the number of peaks in calorimeter projections are calculated in the trigger. The pipeline system is described and the performance of the trigger during the 1997 data-taking period is discussed.

A 40 MHz pipelined trigger for K/sup 0//spl rarr/2/spl pi//sup 0/ decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 experiment, aiming at measuring CP violation in K/sup 0//spl rarr/2/spl pi/ decays. The outputs of the 13340 cells of the 10 m/sup 3/ liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.

Design of the control software for the muon readout system in NA48

We present a brief description of the readout system for the muon detector in the CERN NA48 experiment. This is followed by a discussion of the design of the control software for that system. We particularly emphasize the object-oriented technique of encapsulation. © 1997 American Institute of Physics.

The NA48 Trigger Supervisor design

The design of a hardware pipelined system to collect, monitor and broadcast the trigger information in the CERN NA48 high-rate experiment is presented. Implementation details for a VME-based prototype are also presented. The solutions adopted to cope with a synchronous-asynchronous pipelined trigger system are discussed. >