It is therefore essential that the ATLAS detector cover as much volume as possible across the pseudorapidity distribution η = –ln tan θ/2, where θ is the angle with respect to the proton beam axis. Muons are vital for efficiently triggering on, and thus precisely studying, processes in the electroweak sector such as Higgs, W and Z physics. Almost all triggered muons (blue histogram) are “good” muons (red). Good muons The pseudorapidity distribution of muon candidates passing the level-1 ATLAS trigger with p T > 20 GeV from 2017 Run-2 data, showing the regions expected to be rejected using the NSW in Run 3 and beyond (orange).
If the original chambers were used for the HL-LHC, it would lead to a loss in the efficiency and resolution of muon reconstruction. Another issue for the ATLAS experiment is that the performance of its muon tracking chambers, particularly in the end-cap regions of the detector, degrades with increasing particle rates. The ATLAS experiment, like others at the LHC, is undergoing major upgrades for the new LHC era.Ĭoping with very high interaction rates while maintaining low transverse-momentum (p T) thresholds for triggering on electrons and muons from the targeted physics processes will be extremely challenging at the HL-LHC. This corresponds to 140–200 simultaneous interactions per LHC bunch crossing (“pileup”), which is three to four times the Run-3 expectation and up to eight times above the original LHC design value. After the next shutdown, currently foreseen in 2025–2027, the High-Luminosity LHC (HL-LHC) will run at luminosities of 5–7 × 10 34 cm –2s –1. Following the ongoing 2019–2022 long shutdown, the LHC is expected to operate during Run 3 at close to its design of 7 TeV per beam and at luminosities more than double the original design.
The Large Hadron Collider (LHC) complex is being upgraded to significantly extend its scientific reach. On the right is NSW-C where, at the time of the photograph in July 2021, only a few sectors had been installed. Revolutions The first of the ATLAS New Small Wheels (NSW-A) ready for transport to Point 1 of the LHC. New muon end-cap wheels currently being installed in the ATLAS detector will provide precision tracking and triggering at high rates for Run 3 and beyond.
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