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LumiDays 25
No full text• including the systematic. uncertainties associated w/ DOROS-
BPM performance limitations, e.g. non-reproducibility of the
BPM length scale, their response to beam-beam deflections and
their apparent out-of-plane couplin
Multiplicity and net-electric charge fluctuations in central Ar+Sc interactions at 13A, 19A, 30A, 40A, 75A, and 150A GeV=c beam momenta measured by NA61/SHINE at the CERN SPS
No full textThis paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13A, 19A, 30A, 40A, 75A, and 150A GeV=c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the Epos1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance.This paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13A, 19A, 30A, 40A, 75A, and 150A GeV/c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the EPOS1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance
Experience with the alpaka performance portability library in the CMS software
No full textTo achieve better computational efficiency and exploit a wider range of computing resources, the CMS software framework (CMSSW) has been extended to offload part of the physics reconstruction to NVIDIA GPUs. To support additional back-ends, as well to avoid the need to write, validate and maintain a separate implementation of the reconstruction algorithms for each back-end, CMS has adopted the Alpaka performance portability library.
Alpaka (Abstraction Library for Parallel Kernel Acceleration) is a header-only C++ library that provides performance portability across different back-ends, abstracting the underlying levels of parallelism. It supports serial and parallel execution on CPUs, and extremely parallel execution on NVIDIA, AMD and Intel GPUs.
This contribution will show how Alpaka is used in the CMS software to develop and maintain a single code base; to use different toolchains to build the code for each supported back-end, and link them into a single application; to seamlessly select the best back-end at runtime, and implement portable reconstruction algorithms that run efficiently on CPUs and GPUs from different vendors. It will describe the validation and deployment of the Alpaka-based implementation in the CMS High Level Trigger, and highlight how it achieves near-native performance
Power distribution over the wafer-scale monolithic pixel detector — MOSAIX for ALICE ITS3
No full textFor the LS3 ALICE ITS3 upgrade the detector material budget reduction has been pushed to the limit by proposing a system composed almost exclusively of silicon wafer thinned down to 50μm. This improves performance, but adds complexity to the ASIC design. It requires a wafer-scale module with embedded power delivery network and on-chip data transfer, which were usually done through flexible printed circuit cable.This contribution covers different aspects of the power delivery network design for a wafer-scale detector. It describes the difficulties, shows possible solutions and presents the power scheme design of the full-size ITS3 sensor prototype MOSAIX
The new laser calibration system of the ATLAS hadron calorimeter for High Luminosity LHC
No full textThe research project was developed within the framework of the upgrade of TileCal, the ATLAS central hadron calorimeter, for the HL-LHC (High Luminosity Large Hadron Collider) phase. ATLAS is a general-purpose detector at LHC, CERN, which focuses on studying the Standard Model of particle physics and searching for physics beyond the Standard Model. TileCal is a sampling calorimeter composed of alternating steel layers as absorber material and plastic scintillator tiles as active material. The light produced by the incoming particles interacting with the scintillating tiles is guided through wavelength-shifting fibers to photomultiplier tubes (PMTs). This thesis work is focused on the laser calibration system, which ensure TileCal performance stability for calibrating the response of PMTs. In particularly, it is focused on the preparation of a new optical line, whose main change with respect to the current laser system is the introduction of an adjustable continuous light component superimposed to the pulsed laser light and mixed by an integrating sphere, to better reproduce the PMT operating conditions during pp collisions and to allow for calibrating the PMT response to laser pulses at different level of average anode current. The original contribution of this thesis to the project consisted in defining a geometry for the new optical line. A sequence of measurements to assess light transmission stability and efficiency was performed by using monitors located along the optical line in two setups, in Pisa and at CERN. The results described in this thesis work were discussed with an official ATLAS review committee, which approved the implementation of the project as part of the TileCal upgrade
ATLAS QCD jet measurements
No full textThis article presents a recent QCD measurement of the jet cross-section ratios from the ATLAS experiment at CERN’s Large Hadron Collider, using proton–proton collisions at a center-of-mass energy of 13 TeV. The jet cross-section ratios are derived from multi-differential particle-level cross-sections for several inclusive jet multiplicities bins for at least 2, 3, 4, and 5 jets. These ratios improve sensitivity to the strong coupling parameter while reduce sensitivity to uncorrelated systematic uncertainties and parton distribution functions. The three-to-two jet cross-section ratio is reported for the first time at 13 TeV center-of-mass energy. Additionally, higher jet multiplicity ratios are measured experimentally for the first time, providing a crucial reference for future theoretical developments in high-precision QCD predictions involving multiple jets
Non-identical particle femtoscopy of pairs containing deuteron and interaction studies of nucleons with strange matter
No full textThis thesis focuses on three main research topics. First, it investigates the space-time properties and production mechanism of light nuclei in relativistic heavy ion collisions where quark-gluon plasma is present. Second, it studies the dynamics and interaction of simple hadrons with composite objects (deuterons). Third, it measures the scattering parameters of the strong interaction between the lightest strange meson and single and bound nucleons. The method used in this thesis to investigate the aforementioned topics is known as femtoscopy, which examines two-particle correlations in momentum space. This work presents the momentum correlations measured with the ALICE detector in Pb--Pb collisions at a collision energy of = 5.02 TeV. It focuses on the measurement and interpretation of femtoscopic correlations between various particle pairs, including pions and deuterons, protons and deuterons, kaons and protons, and kaons and deuterons. All of these pairs can be adequately described by interactions involving both Coulomb and strong forces which are determined using various techniques such as resolving Schrdinger equations, numerical parametrization, two- and three-body approaches, including higher order partial waves. The study determines the femtoscopic source sizes of non-identical two-particle pairs across different collision centralities. Notably, the piondeuteron and protondeuteron studies provide the first measurements of deuteron femtoscopic source sizes in PbPb collisions. This measurement has not been previously possible in direct deuterondeuteron studies due to insufficient data. As a result, this thesis offers unique values for the homogeneity lengths of composite objects. These values are further compared with those of simpler particles, such as pions and protons, to investigate their collective flow behavior, which is the driving force behind femtoscopic source dynamics. The protondeuteron and kaonproton studies provide the first experimental evidence of effects expected in large femtoscopic sources. Specifically, the protondeuteron study indicates a reduced impact of three-body dynamics, as the data can be well described by both two- and three-body interactions involving the underlying nucleons of the pair. In contrast, the kaonproton study demonstrates that, in heavy-ion collision sources, coupled channel effects play a negligible role in determining the correlation functions. Furthermore, the kaonproton and kaondeuteron studies present the first measurements of their scattering parameters using femtoscopic techniques. The measurement of the kaondeuteron scattering length for the strong interaction is the first of its kind. This study opens the door to determining isospin-dependent parameters in the fundamental strangeness sector, which also enables insights into the kaonneutron interaction—an interaction that is difficult to investigate experimentally due to the neutron's lack of charge. All the measured parameters are compared with expectations and previous measurements when available. This thesis provides also several insights into scaling of non-identical particles and future directions in studies using the femtoscopy technique
The ATLAS ITk Strip Detector System for the Phase-II LHC Upgrade.
No full textATLAS is currently preparing for the HL-LHC upgrade, with an all-silicon Inner Tracker (ITk) that will replace the current Inner Detector. The ITk will feature a pixel detector surrounded by a strip detector, with the strip system consisting of 4 barrel layers and two endcaps with 6 disks each. After completion of final design reviews in key areas, such as Sensors, Modules, Front-End electronics and ASICs, a large scale prototyping program has been completed in all areas successfully. We present an overview of the Strip System, and highlight the final design choices of sensors, module designs and ASICs. We will summarize results achieved during prototyping and the current status of production and pre-production on various detector components, with an emphasis on QA and QC procedures