The new hardware trigger processor at NA62 experiment: Status of the System and First Results

¹ INFN Roma1, Rome/ Italy
² Sapienza Università, Rome/ Italy
³ CERN Geneva/ Switzerland
⁴ INFN Roma Tor Vergata, Rome/ Italy
⁵ Univ. Autonoma de San Luis Potosi, San Luis Potosi/ Mexico

^* e-mail: ottorino.frezza@roma1.infn.it

Published online: 7 October 2025

Abstract

The NA62 experiment is designed to study rare and ultra-rare kaon decays using a decay-in-flight technique. The Trigger and Data Acquisition (TDAQ) system of NA62 is multi-level, making it critically dependent on the performance of the inter-level network. To manage the huge amount of data produced by the detectors, three levels of triggers are employed. The first level L0TP, implemented using an FPGA device, has been in operation since the start of data taking in 2016. In order to increase the efficiency of the system and implement additional algorithms, an upgraded system (L0TP+) was developed starting in 2018. This upgrade avails itself of a high-end FPGA available on the market, offering more computing power, larger local memory and higher transmission bandwidth. We have planned tests for a new trigger algorithm that implements quadrant-based logic for the veto systems. This new approach is expected to improve the main trigger efficiency by several percent. Extensive tests were conducted using a parasitic setup that included a set of Network TAPs and a commodity server, allowing for proficient comparison of trigger decisions on an event-by-event basis. The experience gained from this parasitic mode operation can be leveraged for the next data-taking period as a development setup to implement additional features, thereby accelerating the TDAQ upgrade. After the testing period, the new system has been adopted as the online processor since 2023. Preliminary results on the efficiency of the new system will be reported. Integration with the new AI-based FPGA-RICH system, which performs online partial particle identification, will also be discussed.