More Like this

1. Joint ATLAS/CMS ZDC upgrade project for the High Luminosity LHC

   https://doi.org/10.1051/epjconf/202327605003  

   Longo, Riccardo (January 2023, EPJ Web of Conferences)

   Kim, Y.; Moon, D.H. (Ed.)

   The High Luminosity LHC (HL-LHC) provides the opportunity to study heavy ion, proton-nucleus, photon-nucleus and photon-photon collisions with unprecedented luminosities at the TeV scale. The LHC heavy ion community has mapped out an extensive range of physics measurements at the HLLHC that will push forward our understanding of both QCD, QED and even electroweak physics. The measurement of forward neutrons and photons in Zero Degree Calorimeters (ZDCs) is essential for event classification and triggering. In order to reach the required luminosities, the LHC interaction regions will be redesigned, necessitating the need to build new ZDCs that will be both narrower and much more radiation tolerant. This challenge motivated the formation of a joint project between ATLAS and CMS to build new ZDCs for Run 4, JZCaP. The ZDCs are based on radiation-hard fused silica rods that produce Cherenkov light. These rods have been developed by Heraeus Quartzglas in collaboration with JZCaP and the LHC BRAN and FLUKA groups. The Run 4 ZDCs (HL-ZDCs) are the first joint detector project between CMS and ATLAS. This talk will present the capabilities of the new ZDCs and recent R&D highlights. 

   more » « less
2. Collectivity in ultra-peripheral heavy-ion collisions

   https://doi.org/10.1051/epjconf/202327601002  

   Shen, Chun; Zhao, Wenbin; Schenke, Björn (January 2023, EPJ Web of Conferences)

   Kim, Y.; Moon, D.H. (Ed.)

   We present full (3+1 )D dynamical simulations to study collective behavior in ultra-peripheral nucleus-nucleus collisions (UPC) at the Large Hadron Collider (LHC) with the 3DGlauber+MUSIC+UrQMD framework [1, 2]. By extrapolating from asymmetric p+Pb collisions, we simulate a quasi-real photon γ* interacting with the Pb nucleus in an ultra-peripheral collision at the LHC, assuming strong final-state effects. We study the elliptic flow hierarchy between p+Pb and γ*+Pb collisions, which is dominated by the difference in longitudinal flow decorrelations. Our theoretical framework provides a quantitative tool to study collectivity in small asymmetric collision systems at current and future collider experiments. 

   more » « less
3. ALICE upgrades during the LHC Long Shutdown 2

   https://doi.org/10.1088/1748-0221/19/05/P05062  

   Acharya, S; Acosta_Hernandez, R; Adamová, D; Adler, A; Adolfsson, J; Agguiaro, D; Aglieri_Rinella, G; Agnello, M; Agnese, F; Agrawal, N; et al (May 2024, Journal of Instrumentation)

   Abstract A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature. 

   more » « less
4. The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3

   https://doi.org/10.1088/1748-0221/19/05/P05063  

   Aad, G; Abbott, B; Abbott, DC; Abdallah, J; Abeling, K; Abidi, SH; Aboulhorma, A; Abovyan, S; Abramowicz, H; Abreu, H; et al (May 2024, Journal of Instrumentation)

   Abstract The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector. 

   more » « less
5. The ATLAS trigger system for LHC Run 3 and trigger performance in 2022

   https://doi.org/10.1088/1748-0221/19/06/P06029  

   Aad, G; Aakvaag, E; Abbott, B; Abeling, K; Abicht, NJ; Abidi, SH; Aboulhorma, A; Abramowicz, H; Abreu, H; Abulaiti, Y; et al (June 2024, Journal of Instrumentation)

   Abstract The ATLAS trigger system is a crucial component of the ATLAS experiment at the LHC. It is responsible for selecting events in line with the ATLAS physics programme. This paper presents an overview of the changes to the trigger and data acquisition system during the second long shutdown of the LHC, and shows the performance of the trigger system and its components in the proton-proton collisions during the 2022 commissioning period as well as its expected performance in proton-proton and heavy-ion collisions for the remainder of the third LHC data-taking period (2022–2025). 

   more » « less