Scientific article
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Improving topological cluster reconstruction using calorimeter cell timing in ATLAS

ContributorsATLAS Collaboration
Publication date2024
First online date2024-05-03
Abstract

Clusters of topologically connected calorimeter cells around cells with large absolute signal-to-noise ratio (topo-clusters) are the basis for calorimeter signal reconstruction in the ATLAS experiment. Topological cell clustering has proven performant in LHC Runs 1 and 2. It is, however, susceptible to out-of-time pile-up of signals from soft collisions outside the 25 ns proton-bunch-crossing window associated with the event’s hard collision. To reduce this effect, a calorimeter-cell timing criterion was added to the signal-to-noise ratio requirement in the clustering algorithm. Multiple versions of this criterion were tested by reconstructing hadronic signals in simulated events and Run 2 ATLAS data. The preferred version is found to reduce the out-of-time pile-up jet multiplicity by ${\sim }50\%$ for jet $p_{\textrm{T}}\sim 20$ GeV and by ${\sim }80\%$ for jet $p_{\textrm{T}} \gtrsim 50$ GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for $20< p_{\textrm{T}} < 30$ GeV. Pile-up is also suppressed for other physics objects based on topo-clusters (electrons, photons, $\tau $-leptons), reducing the overall event size on disk by about $6\%$ in early Run 3 pile-up conditions. Offline reconstruction for Run 3 includes the timing requirement.

Keywords
  • Cluster: topological
  • Jet: multiplicity
  • Pile-up
  • Calorimeter
  • ATLAS
  • Performance
  • Data analysis method
  • Noise
  • Jet: energy resolution
Citation (ISO format)
ATLAS Collaboration. Improving topological cluster reconstruction using calorimeter cell timing in ATLAS. In: European physical journal. C, Particles and fields, 2024, vol. 84, n° 5. doi: 10.1140/epjc/s10052-024-12657-1
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Article (Published version)
Identifiers
Journal ISSN1434-6044
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Creation05/05/2026 08:32:32
First validation05/05/2026 08:39:24
Update05/05/2026 08:39:24
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