Proposal of the Fuzzy Trigger for the Surface Detector of the Pierre Auger Observatory

The standard first level triggers in the surface detectors [analyzing data in the field-programmable gate array (FPGA) just after the digitization in analog to digital converters (ADCs)] of the Pierre Auger Observatory were developed when FPGA was relatively simple and additionally expensive. A huge progress in electronics allows an implementation of very sophisticated mathematical algorithms in very powerful (a lot of FPGA fabric, embedded memories, and digital signal processing (DSP) blocks with very fast embedded multipliers) and relatively inexpensive FPGAs. A fuzzy logic (FL) is an alternative approach for a trigger based on a discrete cosine transform or artificial neural networks developed for the surface detector of the Pierre Auger Observatory. The aim of this article is to report on the trigger design that would allow one to distinguish the signal profiles from the Auger photo-multipliers (PMTs) of the water Cherenkov detectors originating from the neutrino-induced atmospheric showers with a high background of the proton showers. The algorithm has been successfully implemented in CycloneV and Arria10 FPGAs with reasonable resource occupancy and sufficient margin of a registered performance by 120 MHz sampling frequency. The FL trigger may support existing triggers in the Auger surface detector being optimized to identify neutrino-generated showers.