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Boosting the precision of the top quark mass measurement with ATLAS
No full textThe top quark mass is one of the key fundamental parameters of the Standard Model that must be determined experimentally. Its value is essential for testing the self-consistency of the Standard Model. This seminar presents a new measurement of the top quark mass conducted by ATLAS using the full Run 2 proton-proton dataset at 13 TeV. The measurement targets top-antitop-quark pair events where the hadronically decaying top quark has high transverse momentum and is reconstructed as a large-radius jet. A simultaneous fit is performed to the mean of the invariant mass of the large-radius jets and two additional kinematic observables that target the reduction of systematic uncertainties relating to the Jet Energy Scale and Monte Carlo modelling. This results in the most precise ATLAS top quark mass measurement from a single channel to date, with a total uncertainty of 0.53 GeV.
Refreshments will be served at 10h30</p
EOS 2025 Workshop
No full textIn this talk, we want to share our experiences of EOS at IHEP, including migration from CentOS 7 to Almalinux 9, construction of Alice EOS, and dual-site deployment of LHCb T1 EOS
Extension and first application of the ABCDisCo method with LHC data: ABCDisCoTEC
No full textThe ``ABCD method'' provides a reliable framework to estimate backgrounds using observed data by partitioning events into one signal-enhanced region (A) and three background-enhanced control regions (B, C, and D) via two statistically independent variables. In practice, even slight correlations between the two variables can significantly undermine the method's performance. Thus, choosing appropriate variables by hand can present a formidable challenge, especially when background and signal differ only subtly. To address this issue, the ABCDisCo method (ABCD with distance correlation) was developed to construct two artificial variables from the output scores of a neural network trained to maximize signal-background discrimination while minimizing correlations using the distance correlation measure. However, relying solely on minimizing the distance correlation can introduce undesirable characteristics in the resulting distributions, which may compromise the validity of the background prediction obtained using this method. The ABCDisCo training enhanced with closure (ABCDisCoTEC) method is introduced to provide a novel solution to this issue by directly minimizing the nonclosure, expressed as a dedicated differentiable loss term. This extended method is applied to a data set of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS detector at the CERN LHC. Additionally, given the complexity of the minimization problem with constraints on multiple loss terms, the modified differential method of multipliers is applied and shown to greatly improve the stability and robustness of the ABCDisCoTEC method, compared to grid search hyperparameter optimization procedures
Embedding the Timepix4 in Micro-Pattern Gaseous Detectors
No full textThe combination of Micro-Pattern Gaseous Detectors (MPGDs) and pixel charge readout enables specific experimental opportunities. Using the Timepix4 for the readout is advantageous because of its size (around 7 cm^2 active area) and its Through Silicon Vias. The latter enables to connect to the Timepix4 from the back side. Thus, it can be tiled on four sides, allowing it to cover large areas without loss of active area. Here, the first results of reading out MPGDs with the Timepix4 are presented. Measurements with a Gas Electron Multiplier (GEM) detector show that event selection based on geometrical parameters of the interaction is possible, X-ray imaging studies can be performed, as well as energy and time-resolved measurements. In parallel, the embedding of a Timepix4 into a micro-resistive Well (uRWell) amplification structure is explored. The first mechanical tests have been successful. The status of the electrical functionality is presented, as well as simulation studies on the signal induction in such a device
Exotic Hadrons from Hidden Charm to Doubly Charmed Mesons
No full textIn 1964, proposing quarks to describe the known mesons and baryons as (q\bar q) and (qqq) states, Murray Gell-Mann suggested the possible existence of further meson and baryon configurations: tetraquarks (qq \bar q\bar q) and pentaquarks (qqqq \bar q). The first unexpected hadron, the X(3872), was discovered by BELLE in 2003, confirmed by BABAR and seen in many other High Energy experiments. Since then, a wealth of Exotic Hadrons have been observed, mesons and baryons that cannot be described by the classical Gell-Mann configurations. In the seminar, I will illustrate the phenomenology of the first exotic hadrons discovered, the attempts to include them in the Standard Theory and the predicted, still missing, particles needed to complete the scheme.</p
CMS flavor physics projections for the update of the European Strategy for Particle Physics
No full textProjections of the CMS experiment's sensitivity at the HL-LHC to various flavour physics observables are presented. The results are based on measurements from the dataset collected by CMS during LHC Run 2 in proton-proton collisions at a center-of-mass energy of 13 TeV. The projections are derived for integrated luminosities of 2000 and 3000 fb, assuming different scenarios for the evolution of systematic uncertaintie
CERN Tape Archive Workshop : CTA 2025
No full textCTA has been in operation at DESY for nearly two years, during which time additional experiments have been integrated, and over 80PB of data has been written to tape. This presentation will provide an overview of recent developments, along with insights and experiences from running dCache+CTA so fa
CERN Tape Archive Workshop : CTA 2025
No full textOperating the CERN Tape Archive all year-round does not come without surprises and challenges: massive recall campaigns, peak system throughput for archival during the data tacking period and (not so) transparent upgrades to critical services we depend on push the system to the limits, popping some nuts and bolts from time to time.
In this presentation, we will share insights gained from challenges such as temporary network disconnects and hardware problems. We will also discuss the procedures we have developed to mitigate these issues while working towards long term solutions
Carbon, Power, and Sustainability in ATLAS Computing
No full textThe ATLAS Collaboration operates a large, distributed computing infrastructure: almost 1M cores of computing and almost 1 EB of data are distributed over about 100 computing sites worldwide. These resources contribute significantly to the total carbon footprint of the experiment, and they are expected to grow by a large factor as a part of the experimental upgrades for the HL-LHC at the end of the decade. This contribution describes various efforts to understand, monitor, and reduce the carbon footprint of the distributed computing of the experiment. This includes efforts to construct a full life-cycle assessment model for the carbon impact of ATLAS distributed computing, all with the goal of making recommendations for sites to reduce their carbon footprint for the HL-LHC