The NA62 experiment at the CERN SPS aims to measure the branching ratio of the very rare kaon decay K + → π + νν, collecting ∼ 100 events with a 10% background to make a stringent test of the Standard Model. The calorimeter level 0 trigger is used to suppress one of the main backgrounds, the K + → π + π 0 decay, and to select events with a π + in the final state. The calorimeter level 0 trigger identifies clusters in the electromagnetic and hadronic calorimeters. It prepares timeordered lists of reconstructed clusters together with the arrival time, position, and energy measurements of each cluster. It also provides trigger decisions based on complex combinations of energy and cluster multiplicity. The main parameters of the trigger processor are the high design hit rate (30 MHz) and the required single cluster time resolution (1.5 ns). The calorimeter trigger processor is a parallel system composed of 37 boards, 111 mezzanines and 221 high-performance programmable devices housed in three 9U crates. The design, operation and performances of the calorimeter level 0 trigger are presented.

The NA62 experiment at the CERN SPS aims to measure the branching ratio of the very rare kaon decay K + → π + ν ν ¯ . The Calorimetric Level 0 Trigger identifies clusters in the electromagnetic and hadronic calorimeters. Along with the trigger data sent to the L0 Trigger Processor, readout data is collected to be sent to the L1 software trigger. In this work we present the novel implementation of the readout data collection and forwarding system in the multiple layers of the calorimetric trigger structure. We will also present the commissioning of the system and the performance evaluation on current data taking.

The NA62 experiment at the CERN SPS aims at measuring the branching ratio of the very rare kaon decay K + → π + ν ν (expected 10 −10 ) with a 10% background. Since an high-intensity kaon beam is required to collect enough statistics, the Level-0 trigger plays a fundamental role in both the background rejection and in the particle identification. The calorimetric trigger collects data from various calorimeters and it is able to identify clusters of energy deposit and determine their position, fine-time and energy. This paper describes the trigger system setup during the 2016 physics data taking. A newly implemented cluster counting algorithm is also presented. K: Calorimeters; Digital electronic circuits; Trigger algorithms; Trigger concepts and systems (hardware and software) 1Corresponding author.