Abstract
The aim of the NA62 experiment is to study the extreme rare kaon decay K+ ? π+vv and to measure its branching ratio with a 10% accuracy. In order to do so, a very high intensity beam from the CERN SPS is used to produce charged kaons whose decay products are detected by many detectors installed along a 60 m decay region. The NA62 Data Acquisition system (DAQ) exploits a multi-level trigger system; following a Level0 (L0) trigger decision, 1 MHz data rate from about 60 sources is read by a PC-farm, the partial event is built and then passed through a series of Level1 (L1) algorithms to further reduce the trigger rate. Events passing this level are completed with the missing, larger, data sources (~400 sources) at the rate of 100 KHz. The DAQ is built around a high performance ethernet network interconnecting the detectors to a farm of 30 servers. After an overall description of the system design and the main implementation choices that allowed to reach the required performance and functionality, this paper describes the overall behaviour of the DAQ in the 2017 data taking period. It then concludes with an outlook of possible improvements and upgrades that may be applied to the system in the future.
Highlights
The NA62 experimental apparatus [1], located at the CERN Super Proton Synchrotron (SPS), has the main goal to measure the branching ratio of the K+ → π+ννdecay with 10% precision. This process is extremely rare, with an estimated branching ratio of ∼ 10−10 [2]. The search for this process requires a high intensity kaon beam to collect sizable signal event samples, about 1013 kaon decays have to be collected over the data taking period
For that reason the Trigger and the Data Acquisition (TDAQ) chain requires a careful design in order to guarantee a high acceptance for the signal events, while keeping a high rejection of the background
Primitives are sent via UDP packets to the L0 Trigger Processor (L0TP) [4], which can process data coming from a maximum of seven different sources
Summary
The NA62 experimental apparatus [1], located at the CERN Super Proton Synchrotron (SPS), has the main goal to measure the branching ratio of the K+ → π+ννdecay with 10% precision. This process is extremely rare, with an estimated branching ratio of ∼ 10−10 [2]. The search for this process requires a high intensity kaon beam to collect sizable signal event samples, about 1013 kaon decays have to be collected over the data taking period. For that reason the Trigger and the Data Acquisition (TDAQ) chain requires a careful design in order to guarantee a high acceptance for the signal events, while keeping a high rejection of the background
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