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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. [ABSTRACT FROM AUTHOR]

The parallel computing power of commercial Graphics Processing Units (GPUs) is exploited to perform real-time ring fitting at the lowest trigger level using information coming from the Ring Imaging Cherenkov (RICH) detector of the NA62 experiment at CERN. To this purpose, direct GPU communication with a custom FPGA-based board has been used to reduce the data transmission latency. The GPU-based trigger system is currently integrated in the experimental setup of the RICH detector of the NA62 experiment, in order to reconstruct ring-shaped hit patterns. The ring-fitting algorithm running on GPU is fed with raw RICH data only, with no information coming from other detectors, and is able to provide more complex trigger primitives with respect to the simple photodetector hit multiplicity, resulting in a higher selection efficiency. The performance of the system for multi-ring Cherenkov online reconstruction obtained during the NA62 physics run is presented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The NA62 experiment at CERN aims to measure the branching ratio of the ultra-rare charged kaon decay K + → π + ν ν ¯ with a 10% accuracy and with a background contamination at the 10% level. Since the branching ratio of this decay is O (10 −10 ), to fulfill such request one of the main backgrounds, the decay K + → μ + ν (BR ~ 63 % ), must be suppressed by a rejection factor of 4×10 −13 (assuming 10% signal acceptance). This can be partially accomplished using a combination of kinematical cuts (8×10 −6 ) and the different power of penetration through matter of pions and muons (10 −5 ). A further 5×10 −3 suppression factor will be provided by a RICH detector, in a momentum range between 15 and 35 GeV/c. The details of the RICH project as well as the results from test runs performed on a RICH prototype of the same length of the final detector will be presented. The current status of the construction and the description of the final readout and trigger electronics will also be reviewed. [ABSTRACT FROM AUTHOR]

Abstract: A Ring Imaging Cherenkov (RICH) detector is the key element for particle identification in the NA62 experiment at CERN. Its purposes are to distinguish pions from muons in the momentum range from 15GeV/c to 35GeV/c with a muon suppression factor at the 0.5% level, to measure the particle arrival time with better than 100ps resolution and to provide the reference time and a fast signal for the trigger system. This paper describes the updated detector design, the present status of the construction, the final results of a prototype beam test and a possible application of Graphics Processing Units in the NA62 trigger system based on RICH information. [Copyright &y& Elsevier]

The NA62 RICH detector is used for the separation of pions and muons in the momentum range 15–35 GeV/c and is expected to provide a muon suppression factor better than 10^-2. A prototype of the final detector equipped with about 400 PMs (RICH-400 prototype) was built and tested in a dedicated run in 2009. The \pi-\mu separation was tested, as well as the effect of the contamination of the neon radiator with different amounts of oxygen and CO2. The \mu misidentification probability is about 0.7% and the time resolution better than 100 ps in the whole momentum range. We did not observe any absorption of the light due to the contamination of the radiator, however an effect on the ring radius is clearly observed due to the change of the refractive index of the medium. The conclusion of the studies is that the amount of CO2 in the final detector should be known at the 10^-3 level of precision or the quality of the pion identification could be seriously compromised. [ABSTRACT FROM PUBLISHER]

Abstract: The NA62 experiment at CERN, aimed to measure branching fraction (O(10−10)), relies on a Neon based RICH detector for separation, time measurement and level 0 trigger. The experimental requirements for this detector are: a muon contamination in pion samples lower than 5×10−3 in the momentum range 15–35GeV/c and a time resolution on the charged track better than 100ps. A prototype of such a detector was built and tested in 2009; it consists of a full length () Ne filled vessel equipped with a spherical mirror and 414 PMs on its focal plane, located about 17m upstream of the mirror. This prototype was tested at CERN SPS on a positive hadron beam, in the required momentum range, to measure the separation and to confirm the time resolution obtained with a previous prototype; the misidentification probability is about 0.7% and the time resolution is better than 100ps in the whole momentum range. [ABSTRACT FROM AUTHOR]

Abstract: A RICH prototype has been constructed and tested. The detector was cylindrical, 17m long and 60cm diameter, filled with neon gas at atmospheric pressure. A spherical mirror with 17m focal length was used and 96 photomultipliers were placed in the mirror focal plane. The prototype was exposed to a momentum negative beam derived from the CERN SPS in the 2007 fall. The performances of the detector in terms of Cherenkov angle resolution, number of photoelectrons and time resolution are presented. [Copyright &y& Elsevier]