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ATLAS ITk Pixel Detector Overview
No full textIn the high-luminosity era of the Large Hadron Collider, the instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. To cope with the resulting increases in occupancy, bandwidth, and radiation levels, the ATLAS Inner Detector will be replaced by the all-silicon Inner Tracker (ITk). The innermost part of the ITk will consist of a pixel detector, with an active area of about 13 m^2. To meet requirements in terms of radiation hardness, power dissipation, and production yield, several silicon sensor technologies are adopted in the five barrel and endcap layers. The project is moving toward production of components---sensors, module assemblies, mechanical structures, and services. The pixel modules assembled with ITkPixV2 readout chips have been built to evaluate their production rates. Irradiation campaigns have been conducted to evaluate thermal and electrical performance before and after irradiation. A new powering scheme – serial – will be employed in the ITk pixel detector, helping to reduce both the material thickness of the detector and power dissipation. This contribution presents the status of the ITk-pixel project focusing on the lessons learned and the main challenges towards production, from sensors and mechanics structures, and it will summarize the latest results on closest-to-real demonstrators built using module, electric and cooling services prototypes
Measurement of multi-jets and vector boson plus jets production in ATLAS
No full textThe production of multiple jets or vector bosons in association with jets at the LHC provides a unique testing ground for Quantum Chromodynamics (QCD) in the high-energy regime. With the increasing precision of the ATLAS measurements, detailed studies have become possible on observables that probe different aspects of QCD, such as the topological configurations between vector bosons and jets, jet substructure features, and heavy-flavor jet contributions. These measurements also play a key role in improving the precision of the determination of the strong coupling constant. Recent ATLAS results in these areas are presented, offering new insights into QCD dynamics and the performance of state-of-the-art theoretical predictions
Electromagnetic moments of Bi: Probing shell evolution beyond N=126
No full textThe nuclear properties of bismuth isotopes (Z=83), with just one valence proton above the closed spherical shell at Z=82, are expected to be governed by a single unpaired proton. However, already in semimagic 209Bi (Z=83, N=126), the magnetic moment (μ) strongly deviates from the single-particle Schmidt value. A near linear decrease in μ with the increase of N after the N=126 magic number was observed up to N=130. In order to test whether this trend is kept at N > 130 and to reveal the underlying mechanisms, an investigation of 215,217Bi (N=132,134) has been undertaken. The magnetic dipole and electric quadrupole moments of the Iπ=9/2− nuclear ground states in these isotopes have been measured for the first time using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). It has been shown that the linearly decreasing trend of μ(209,211,213Big) is broken in 215,217Bi with a nearly constant value of μ observed. Experimental data have been compared to calculations in the framework of the configuration-interaction shell model with the monopole-based universal VMU+LS interaction. The peculiarities in the behavior of μ(Bi, 9/2−) with increasing neutron number are explained as being due to the shell evolution, change of the neutron orbitals occupancies and strong configuration mixing beyond N=130. Also, the difference in the μ trends for bismuth (Z=83) and astatine (Z=85) isotopes with N > 126 are reproduced by the shell-model calculations. It is shown that monopole interaction plays noticeable role in the description of the peculiarities of the μ behaviour. Additionally, the extension of the application of the VMU interaction to the μ isotopic trends for heavy nuclei is important for further study of the capabilities of this promising version of the shell-model calculations
Measurement of WWbb Production in the Single Lepton Final State with ATLAS at TeV
No full textPrecise measurements of differential cross sections in the process offer an outstandingly rich physics potential at highest precision. The process is theoretically and experimentally well defined, exhibiting sensitivity to Monte Carlo modeling effects as well as to Standard Model parameters. I will report on the first cross section measurements in the single- lepton channel with Run-II data taken by the ATLAS experiment. The analysis comprises three signal regions, focusing on the interference between and processes, the explicit reconstruction of the kinematics of the system and on phase spaces motivated by BSM searches
Search for → ̅ and Measurement of → ̅ in Vector-Boson Fusion Production with the ATLAS Detector
No full textA search for the Standard Model (SM) Higgs boson decaying to a charm quark-antiquark pair ( Hcc ) and a bottom quark-antiquark pair (Hbb) via the vector boson fusion (VBF) production mode is presented using partial Run 2 and partial Run 3 datasets recorded by the ATLAS detector at CERN’s Large Hadron Collider (LHC). The Hcc search combines two datasets: 37.5 fb-1at a center of mass energy of s = 13 TeV from 2018 and 51.5 fb-1 at a center of mass energy of s = 13.6 TeV from 2022 and 2023 resulting in a combined integrated luminosity of 89.4 fb-1. The Hbb measurement is measured simultaneously using 51.5 fb-1 of proton-proton collision data at a center of mass energy of s = 13.6 TeV. The results found by this analysis are also combined with the previous Run 2 measurements of VBF Hbb and VHcc