The NA62 Calorimeter Level 0 Trigger Operation and Performances

Abstract

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.

Performance of the NA62 trigger system

“…The CHOD, NA48-CHOD, and MUV3 define four regions as quadrants, with the MUV3 excluding eight tiles close to the detector centre from the quadrant definition (figure 2). The LKr participates via a dedicated calorimeter L0 trigger system that uses information from groups of channels provided by calorimeter readout modules [10].…”

The NA62 level 0 calorimetric trigger fast readout implementation, commissioning and data taking performances

“…The Calorimetric Level 0 Trigger [6][7][8][9] (L0Calo) 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. L0Calo identifies clusters in the electromagnetic (Liquid Krypton -LKr, Intermediate-Ring Calorimeter -IRC, and the Small-Angle Calorimeter -SAC) and hadronic (two Muon Veto -MUV 1 and 2) calorimeters.…”