Improving topological cluster reconstruction using calorimeter cell timing in ATLAS

Summary, in English

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 ∼50% for jet pT∼20 GeV and by ∼80% for jet pT≳50 GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for 20

• Author: G. Aad; T.P.A. Åkesson; C. Doglioni; P.A. Ekman; V. Hedberg; H. Herde; B. Konya; E. Lytken; R. Poettgen; N.D. Simpson; O. Smirnova; L. Zwalinski
• Department/s: Particle and nuclear physics; Department of Physics; eSSENCE: The e-Science Collaboration
• Publishing year: 2024
• Language: English
• Publication/Series: European Physical Journal C
• Volume: 84
• Issue: 5
• Links: http://dx.doi.org/10.1140/epjc/s10052-024-12657-1
• Document type: Journal article
• Publisher: Springer Nature
• Topic: Subatomic Physics
• Keywords: Calorimeters; Calorimetry; Germanium compounds; Hadrons; Photons; ATLAS experiment; Bunch crossings; Calorimeter cells; Cell clustering; Hadronics; Noise ratio; Pile-ups; Signal to noise; Signals reconstruction; Topo; Topology
• Status: Published
• ISBN/ISSN/Other: ISSN: 1434-6044