IOSCO: Its Mission and Achievement

The origins of the International Organization of Securities Com- missions (IOSCO) lie in the Americas. In 1974, nations of the West- em Hemisphere, largely under the leadership of the United States, organized the InterAmerican Association of Securities Commissions to provide a forum for consideration of securities regulation matters of common interest and to assist capital formation in the Western Hemisphere. Nine years later the organization transformed itself into a world-wide organization and was incorporated by an act of the Que- bec Parliament as a non-profit corporation under Quebec law. A sec- retariat was established in Montreal, a recognition of the expanded scope of the organization. IOSCO perceives the transition from a Western hemisphere endeavor to a world-wide one not as the succes- sion of one organization by another, but rather as a continuum; for instance, it numbers its annual meetings from the inception of the In- terAmerican Association; thus the first meeting of IOSCO in 1987 was called the Twelfth Annual Conference. The 1988 Annual Report was the first published, hence it is difficult to gain much insight into the 1974-1988 activity of the regulators.\u2

IOSCO: Its Mission and Achievement

The origins of the International Organization of Securities Com- missions (IOSCO) lie in the Americas. In 1974, nations of the West- em Hemisphere, largely under the leadership of the United States, organized the InterAmerican Association of Securities Commissions to provide a forum for consideration of securities regulation matters of common interest and to assist capital formation in the Western Hemisphere. Nine years later the organization transformed itself into a world-wide organization and was incorporated by an act of the Que- bec Parliament as a non-profit corporation under Quebec law. A sec- retariat was established in Montreal, a recognition of the expanded scope of the organization. IOSCO perceives the transition from a Western hemisphere endeavor to a world-wide one not as the succes- sion of one organization by another, but rather as a continuum; for instance, it numbers its annual meetings from the inception of the In- terAmerican Association; thus the first meeting of IOSCO in 1987 was called the Twelfth Annual Conference. The 1988 Annual Report was the first published, hence it is difficult to gain much insight into the 1974-1988 activity of the regulators.\u2

The ATLAS trigger system for LHC Run 3 and trigger performance in 2022

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)

Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with theFluka Monte Carlo programme

Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb-1 of LHC proton-proton collision data recorded at √(s) = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ψ → ee and radiative Z-boson decays

Performance and calibration of quark/gluon-jet taggers using 140 fb−1 of pp collisions at √s = 13 TeV with the ATLAS detector

The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using √s = 13 TeV proton–proton collision data with an integrated luminosity of 140 fb-1 collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points

Search for bottom-squark pair production with the ATLAS detector in final states containing Higgs bosons, b -jets and missing transverse momentum

Abstract: The result of a search for the pair production of the lightest supersymmetric partner of the bottom quark b˜1 using 139 fb−1 of proton-proton data collected at s = 13 TeV by the ATLAS detector is reported. In the supersymmetric scenarios considered both of the bottom-squarks decay into a b-quark and the second-lightest neutralino, b˜1→b+χ˜20. Each χ˜20 is assumed to subsequently decay with 100% branching ratio into a Higgs boson (h) like the one in the Standard Model and the lightest neutralino: χ˜20→h+χ˜10. The χ˜10 is assumed to be the lightest supersymmetric particle (LSP) and is stable. Two signal mass configurations are targeted: the first has a constant LSP mass of 60 GeV; and the second has a constant mass difference between the χ˜20 and χ˜10 of 130 GeV. The final states considered contain no charged leptons, three or more b-jets, and large missing transverse momentum. No significant excess of events over the Standard Model background expectation is observed in any of the signal regions considered. Limits at the 95% confidence level are placed in the supersymmetric models considered, and bottom-squarks with mass up to 1.5 TeV are excluded