A muon trigger upgrade with high transverse momentum resolution for the ATLAS detector at the High-Luminosity LHC

Y Horii

doi:10.1088/1748-0221/10/01/c01005

Abstract

The Level-1 trigger for muons of the ATLAS experiment is based on trigger chambers with excellent timing resolution which identify muons coming from a particular beam crossing. To cope with the stringent constraint on the trigger rates expected during phase II of the LHC, the so-called High-Luminosity LHC, it is proposed to include precision tracking chambers in the Level-1 muon trigger for improving the transverse momentum resolution. The rate of a single muon trigger with a transverse momentum threshold of 20 GeV is estimated to be reduced by about a factor of two over the entire pseudorapidity region by introducing the proposed upgrade. An architecture of the electronics includes an additional priority readout chain, which is independent of the standard and asynchronous readout. A demonstrator of the frontend electronics has been developed and an initial test based on cosmic muons shows position resolution measurements consistent with the simulation.

Highlights

Experimental data recorded by the ATLAS experiment in 2012 are used to evaluate the trigger rate reduction by introducing the proposed upgrade [3]
A requirement on the deflection angle evaluated from the track segments reconstructed by the MDT chambers is applied
The priority readout chain is based on time-to-digital converters (TDCs) with a foreseen clock frequency of 80 MHz

Summary

Estimation of a trigger rate reduction

Experimental data recorded by the ATLAS experiment in 2012 are used to evaluate the trigger rate reduction by introducing the proposed upgrade [3]. Events are selected by requiring the Level-1 muon trigger with a pT threshold of 20 GeV. A requirement on the deflection angle evaluated from the track segments reconstructed by the MDT chambers is applied. By introducing the requirement based on the MDT chambers, the accept rate for a Level-1 single muon trigger with a pT threshold of 20 GeV is estimated to be reduced by about a factor of two. SW + Tile (expected Phase I) SW + Tile + Mask (proposed Phase I or II) SW + Tile + Mask + MDT (proposed Phase II). SW + Tile (expected Phase I) SW + Tile + Mask (proposed Phase I or II) SW + Tile + Mask + MDT (proposed Phase II) Offline selected muons forp > 20 GeV. (b) Distributions of the pseudorapidity ηL1 of the Level-1 muon candidates

Technical implementation

Hardware demonstrator and a preliminary test result

Conclusion