Improving topological cluster reconstruction using calorimeter cell timing in ATLAS
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866913343780945920 |
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| author | ATLAS Collaboration |
| author_facet | ATLAS Collaboration |
| contents | 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 $p_\text{T}\sim 20$ GeV and by $\sim$80% for jet $p_\text{T} \gtrsim 50$ GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for $20 < p_\text{T} < 30$ GeV. Pile-up is also suppressed for other physics objects based on topo-clusters (electrons, photons, $τ$-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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2310_16497 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Improving topological cluster reconstruction using calorimeter cell timing in ATLAS ATLAS Collaboration Instrumentation and Detectors High Energy Physics - Experiment 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 $p_\text{T}\sim 20$ GeV and by $\sim$80% for jet $p_\text{T} \gtrsim 50$ GeV, while not disrupting the reconstruction of hadronic signals of interest, and improving the jet energy resolution by up to 5% for $20 < p_\text{T} < 30$ GeV. Pile-up is also suppressed for other physics objects based on topo-clusters (electrons, photons, $τ$-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. |
| title | Improving topological cluster reconstruction using calorimeter cell timing in ATLAS |
| topic | Instrumentation and Detectors High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2310.16497 |