Performance of a First-Level Muon Trigger with High Momentum Resolution Based on the ATLAS MDT Chambers for HL-LHC

TL;DR

This paper presents a new first-level muon trigger concept for the ATLAS experiment at HL-LHC, utilizing MDT chambers for improved momentum resolution and trigger efficiency, based on data from 8 TeV collisions.

Contribution

It introduces a novel muon trigger stage using MDT chambers with extended latency and new electronics, enhancing selectivity and resolution at HL-LHC.

Findings

Achieved better than 4.1% momentum resolution across sectors.

Trigger threshold of 18 GeV is fully efficient for muons above 24 GeV in the barrel.

Demonstrated improved trigger performance using existing MDT chambers.

Abstract

Highly selective first-level triggers are essential to exploit the full physics potential of the ATLAS experiment at High-Luminosity LHC (HL-LHC). The concept for a new muon trigger stage using the precision monitored drift tube (MDT) chambers to significantly improve the selectivity of the first-level muon trigger is presented. It is based on fast track reconstruction in all three layers of the existing MDT chambers, made possible by an extension of the first-level trigger latency to six microseconds and a new MDT read-out electronics required for the higher overall trigger rates at the HL-LHC. Data from $pp$-collisions at $\sqrt{s} = 8\,\mathrm{TeV}$ is used to study the minimal muon transverse momentum resolution that can be obtained using the MDT precision chambers, and to estimate the resolution and efficiency of the MDT-based trigger. A resolution of better than $4.1\%$ is found in all sectors under study. With this resolution, a first-level trigger with a threshold of $18\,\mathrm{GeV}$ becomes fully efficient for muons with a transverse momentum above $24\,\mathrm{GeV}$ in the barrel, and above $20\,\mathrm{GeV}$ in the end-cap region.