An FPGA-based trigger for the search of μ+ → e+7 decay in the MEG experiment

A novel trigger has been set up and it is now operating in the MEG experiment at Paul Scherrer Institut, which aims at searching for the lepton flavour violating decay μ⁺ /spI larr/ e⁺γ with unprecedented sensitivity (10^-13 for the branching ratio). An overview of the trigger architecture is given, as well as a description of the design and the main features of the dedicated boards and their usage. Particular emphasis is laid on the use of Field Programmable Gate Arrays to implement the on-line event selection algorithms needed to achieve the high test capable accidental event rejection while keeping the trigger latency lower 400 ns. Resolutions on selection variables reconstruction are also presented.