TY - JOUR

T1 - Improving topological cluster reconstruction using calorimeter cell timing in ATLAS

AU - The ATLAS collaboration

AU - Barton, A.E.

AU - Bertram, I.A.

AU - Borissov, G.

AU - Bouhova-Thacker, E.V.

AU - Ferguson, Ruby

AU - Ferrando, James

AU - Fox, H.

AU - Hagan, Alina

AU - Henderson, R.C.W.

AU - Jones, R.W.L.

AU - Kartvelishvili, V.

AU - Love, P.A.

AU - Marshall, E.J.

AU - Meng, L.

AU - Muenstermann, D.

AU - Ribaric, N.

AU - Rybacki, K.

AU - Smizanska, M.

AU - Spinali, S.

AU - Wharton, A.M.

PY - 2024/5/3

Y1 - 2024/5/3

N2 - 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 $${\sim }50\%$$ ∼ 50 % for jet $$p_{\textrm{T}}\sim 20$$ p T ∼ 20 GeV and by $${\sim }80\%$$ ∼ 80 % for jet $$p_{\textrm{T}} \gtrsim 50$$ p T ≳ 50 GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for $$20< p_{\textrm{T}} < 30$$ 20 < p T < 30 GeV. Pile-up is also suppressed for other physics objects based on topo-clusters (electrons, photons, $$\tau $$ τ -leptons), reducing the overall event size on disk by about $$6\%$$ 6 % in early Run 3 pile-up conditions. Offline reconstruction for Run 3 includes the timing requirement.

AB - 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 $${\sim }50\%$$ ∼ 50 % for jet $$p_{\textrm{T}}\sim 20$$ p T ∼ 20 GeV and by $${\sim }80\%$$ ∼ 80 % for jet $$p_{\textrm{T}} \gtrsim 50$$ p T ≳ 50 GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for $$20< p_{\textrm{T}} < 30$$ 20 < p T < 30 GeV. Pile-up is also suppressed for other physics objects based on topo-clusters (electrons, photons, $$\tau $$ τ -leptons), reducing the overall event size on disk by about $$6\%$$ 6 % in early Run 3 pile-up conditions. Offline reconstruction for Run 3 includes the timing requirement.

U2 - 10.1140/epjc/s10052-024-12657-1

DO - 10.1140/epjc/s10052-024-12657-1

M3 - Journal article

VL - 84

JO - European Physical Journal C: Particles and Fields

JF - European Physical Journal C: Particles and Fields

SN - 1434-6044

IS - 5

M1 - 455

ER -