..the innermost detector in ALICE, it will operate in a region where the track density could be as high as 50 tracks/cm2.
The SPD consists of two layers of silicon pixel detector modules located around the beam-pipe at an average distances of 39 mm and 76 mm from the beam axis, respectively.
SPD has a key role in the determination of the position of the primary vertex and in the measurement of the impact parameter of secondary tracks originating from the weak decays of strange, charm and beauty particles.
A unique feature of the SPD is its capability to generate a prompt trigger based on an internal fast-OR. Every 100 ns 1200 fast-OR signals are transmitted and processed in a separate processor unit according to a variety of pre-defined trigger algorithms to generate a signal that can contribute to Level 0 trigger decision in the ALICE central trigger processor (CTP) within about 800 ns from the interaction.
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