ATLAS Calorimeter: Run 2 performance and Phase-II upgrades

Abstract

The ATLAS detector was designed and built to study proton-proton collisions produced at the LHC at centre-of-mass energies up to 14 TeV and instantaneous luminosities up to 10 34 cm −2 s −1. A Liquid Argon-lead sampling (LAr) calorimeter is employed as electromagnetic and hadronic calorimeters, except in the barrel region, where a scintillator-steel sampling calorimeter (TileCal) is used as hadronic calorimeter. This presentation gives first an overview of the detector operation and data quality, as well as of the achieved performances of the ATLAS calorimetry system. Additionally the upgrade projects of the ATLAS calorimeter system for the high luminosity phase of the LHC (HL-LHC) are presented. For the HL-LHC, the instantaneous luminosity is expected to increase up to L ≃ 7.5 × 10 34 cm −2 s −1 and the average pileup up to 200 interactions per bunch crossing. The major R&D item is the upgrade of the electronics for both LAr and Tile calorimeters in order to cope with longer latencies of up to 60 µs. The expected radiation doses will exceed the qualification range of the current readout system. The status of the R&D of the lowpower ASICs (pre-amplifier, shaper, ADC, serializer and transmitters) and readout electronics for all the design options is discussed. Moreover, a High Granularity Timing Detector (HGTD) is proposed to be added in front of the LAr calorimeters in the end-cap region (2.4 < |η| < 4.2) for pileup mitigation at Level-0 trigger level and offline reconstruction. The HGTD will correlate the energy deposits in the calorimeter to different proton-proton collision vertices by using TOF information with high time resolution (30 pico-seconds per readout cell) based on the Silicon sensor technologies. The current test beam results are presented in this document as well.

Displaced lepton jet signatures from self-interacting dark matter bound states

“…When doing a bump hunt for B ps , we find about 10 (20) background events for m χ ≈ 80 (150) GeV, if the width of the constructed invariant mass peak is around 10 GeV, coming from the imperfect DLJ energy measurement. Since further improvements on the Run 3 and high luminosity study are expected due to the more control region data and better HCAL resolution [95][96][97], an even better background rejection can be achieved.…”

Study of W Boson Production in Association with Two Jets using Boosted Decision Trees with Data Collected by the ATLAS Detector.

“…In contrast, the liquid argon electromagnetic calorimeter's main function is to entrap all electron and photon energy. The pseudo-rapidity ranges of the electromagnetic calorimeters are |η| < 1.475 for the barrel region, and 1.375 < |η| < 3.2 for the end-caps [15]. To account for energy lost in the inner detector, a pre-sampler detector is used over the |η| < 1.8 range [13].…”