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The W-Si High Precision Preshower Detector of the FASER Experiment at the LHC
No full textFASER is searching for light, weakly-interacting particles at the Large Hadron Collider. The first search for Axion-like particles (ALPs) decaying to a photon pair using data collected in 2022 and 2023 was performed and successfully excluded regions not previously ruled out. To further reduce neutrino background, a new preshower detector will be installed by the end of 2024. The detector is based on a monolithic active pixel sensor in 130 nm SiGe BiCMOS, which will allow resolving the photon pairs interacting in the preshower detector. The final ASICs have been produced in May 2024 and are currently being validated
Performance of the ALICE Zero Degree Calorimeters in LHC Run 3
No full textThe Zero Degree Calorimeters (ZDC) of the ALICE experiment at the LHC were designed to characterize the event and monitor the luminosity in heavy-ion collisions. In order to fully exploit the potential offered by the LHC increased luminosity in Run 3, while preserving the time and charge resolution performance, the ZDC readout system was upgraded to allow the acquisition of all collisions in self-triggered mode without dead time. The presence of electromagnetic dissociation (EMD) processes makes the ZDC operating conditions extremely challenging, raising the readout rate for the channels of the most exposed calorimeters up to 1.4 Mevents/s, compared to an hadronic rate of about 50 Kevents/s sustained by all other detectors. The new acquisition chain is based on a commercial 12 bit digitizer with a sampling rate of 1 GSps, assembled on an FPGA Mezzanine Card. The signals produced by the ZDC channels are digitized, the samples are processed through an FPGA that, thanks to a custom trigger algorithm, flags for readout the relevant portion of the waveform and extracts information such as timing, baseline average and event rate. The system is fully integrated with the ALICE data taking infrastructure and acquired physics data during the 2023 LHC heavy-ion data taking. The architecture of the new readout system, the auto trigger strategy, and the ZDC performance during the 2023 Pb–Pb collisions are presented
Comparison of smoothening flows for the topological charge in QCD-like theories
No full textWe investigate properties of the topological charge for several SU(NC) gauge field ensembles for NC = 4, 5, 6 with a single fermion in the two-index anti-symmetric representation, covering multiple lattice spacings at otherwise approximately constant physical parameters. Comparing the topological charge defined by the Wilson flow and the over-improved DBW2 flow we find that already at small flow times the latter stabilises on discrete values. We provide evidence that as the lattice spacing is lowered the Wilson flow also separates into discrete sectors at earlier flow times. Adopting the DWB2 definition in the remainder of the analysis, we do not see any evidence of fractional topological charges, which could in principle appear at finite lattice spacing
Fast Jet Tagging with MLP-Mixers on FPGAs
No full textWe explore the innovative use of MLP-Mixer models for real-time jet tagging and establish their feasibility on resource-constrained hardware like FPGAs. MLP-Mixers excel in processing sequences of jet constituents, achieving state-of-the-art performance on datasets mimicking Large Hadron Collider conditions. By using advanced optimization techniques such as High-Granularity Quantization and Distributed Arithmetic, we achieve unprecedented efficiency. These models match or surpass the accuracy of previous architectures, reduce hardware resource usage by up to 97%, double the throughput, and half the latency. Additionally, non-permutation-invariant architectures enable smart feature prioritization and efficient FPGA deployment, setting a new benchmark for machine learning in real-time data processing at particle colliders
Logarithmic angle-dependent gauge transformations at null infinity
No full textLogarithmic angle-dependent gauge transformations are symmetries of electromagnetism that are canonically conjugate to the standard angle-dependent transformations. They were exhibited a few years ago at spatial infinity. In this paper, we derive their explicit form at null infinity. We also derive the expression there of the associated "conserved" surface integrals. To that end, we provide a comprehensive analysis of the behaviour of the electromagnetic vector potential in the vicinity of null infinity for generic initial conditions given on a Cauchy hypersurface. This behaviour is given by a polylogarithmic expansion involving both gauge-invariant logarithmic terms also present in the field strengths and gauge-variant logarithmic terms with physical content, which we identify. We show on which explicit terms, and how, do the logarithmic angle-dependent gauge transformations act. Other results of this paper are a derivation of the matching conditions for the Goldstone boson and for the conserved charges of the angle-dependent asymptotic symmetries, as well as a clarification of a misconception concerning the non-existence of these angle-dependent charges in the presence of logarithms at null infinity. We also briefly comment on higher spacetime dimensions
Recent measurements of diboson production (including VBS)
No full textMeasurement of diboson events is a unique venue at the LHC, offering precision test of SM QCD and EW predictions at unprecedented accuracies relevant to this sector, and sensitive probe of the non-Abelian structure of SM EW theory, leading to stringent constraints on Effective Field Theory wilson coefficients. Measurement of rare processes in the electroweak sector poses an unprecedented stringent test of the SM theory, and in particular offers unique sensitivity to study the electroweak symmetry breaking and the quartic boson self-couplings (VBS processes). In addition to cross-section measurements, systematic study of boson polarization states in VBS processes is being actively pursued to hopefully bring further sensitivity and uncover deeper insights. This talk will summarize recent achievements from the LHC on this topic
Pion and kaon pair production in double-gap events in ALICE Run 3
No full textThe ALICE detector at the LHC has undergone a major upgrade in the long shutdown 2019–2021 to be able to take data at much-increased rates in Runs 3 and 4. The upgrades of the detector systems used for analysing double-gap events are described, and the improvement in data taking capability for such double-gap events is presented.The ALICE detector at the LHC has undergone a major upgrade in the long shutdown 2019-2021 to be able to take data at much-increased rates in Runs 3 and 4. The upgrades of the detector systems used for analysing double gap events are described, and the improvement in data taking capability for such double gap events is presented
Tracing Different Types of Local Economic Benefits of RIs: The Case Study of LHC
No full textCERN is operating the world’s largest particle accelerator complex in the world. The interconnection of versatile particle accelerators working with different particle beams at different intensities and energies continue to attract scientists and engineers from all over the world. The socio-economic effects generated by the presence of in the region are manifold. They include, but are not limited to consumer spending, real-estate investments and local business and services activities, investments in education, leisure activities and tourism, urban development and tax contributions. This chapter traces different local socio-economic effects of concentrating a large number of people around a research infrastructure
Efficient high performance computing with the ALICE Event Processing Nodes GPU-based farm
No full textDue to the increase of data volumes expected for the LHC Run 3 and Run 4, the ALICE Collaboration designed and deployed a new, energy efficient, computing model to run Online and Offline O data processing within a single software framework. The ALICE O Event Processing Nodes (EPN) project performs online data reconstruction using GPUs (Graphic Processing Units) instead of CPUs and applies an efficient, entropy-based, online data compression to cope with PbPb collision data at a 50 kHz hadronic interaction rate. Also, the O EPN farm infrastructure features an energy efficient, environmentally friendly, adiabatic cooling system which allows for operational and capital cost savings