Dr Elizabeth Gallas

Abstract:

A summary of the constraints from searches performed by the ATLAS collaboration for the electroweak production of charginos and neutralinos is presented. Results from eight separate ATLAS searches are considered, each using 140 fb⁻¹ of proton-proton data at a centre-of-mass energy of √𝑠 = 13 TeV collected at the Large Hadron Collider during its second data-taking run. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, where R-parity conservation is assumed and the lightest supersymmetric particle is assumed to be the lightest neutralino. Constraints from previous electroweak, flavour and dark matter related measurements are also considered. The results are presented in terms of constraints on supersymmetric particle masses and are compared with limits from simplified models. Also shown is the impact of ATLAS searches on parameters such as the dark matter relic density and the spin-dependent and spin-independent scattering cross-sections targeted by direct dark matter detection experiments. The Higgs boson and Z boson ‘funnel regions’, where a low-mass neutralino would not oversaturate the dark matter relic abundance, are almost completely excluded by the considered constraints. Example spectra for non-excluded supersymmetric models with light charginos and neutralinos are also presented.

Abstract:

A search for CP violation in the decay kinematics and vector-boson fusion production of the Higgs boson is performed in the H → ZZ* → 4ℓ (ℓ = e, μ) decay channel. The results are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb−1. Matrix element-based optimal observables are used to constrain CP-odd couplings beyond the Standard Model in the framework of Standard Model effective field theory expressed in the Warsaw and Higgs bases. Differential fiducial cross-section measurements of the optimal observables are also performed, and a new fiducial cross-section measurement for vector-boson-fusion production is provided. All measurements are in agreement with the Standard Model prediction of a CP-even Higgs boson.

Abstract:

The ATLAS Eventlndex is the global catalogue of all ATLAS real and simulated events. During the LHC long shutdown between Run 2 (20152018) and Run 3 (2022-2025) all its components were substantially revised and a new system was deployed for the start of Run 3 in Spring 2022. The new core storage system, based on HBase tables with a SQL interface provided by Phoenix, allows much faster data ingestion rates and scales much better than the old one to the data rates expected for the end of Run 3 and beyond. All user interfaces were also revised and a new command-line interface and web services were also deployed. The new system was initially populated with all existing data relative to Run 1 and Run 2 datasets, and then put online to receive Run 3 data in real time. After extensive testing, the old system, which ran in parallel to the new one for a few months, was finally switched off in October 2022. This paper describes the new system, the move of all existing data from the old to the new storage schemas and the operational experience gathered so far

Abstract:

The ATLAS EventIndex is a global catalogue of the events collected, processed or generated by the ATLAS experiment. The system was upgraded in advance of LHC Run 3, with a migration of the Run 1 and Run 2 data from HDFS MapFiles to HBase tables with a Phoenix interface. Two frameworks for testing functionality and performance of the new system have been developed. There are two types of tests running. First, the functional test that must check the correct functioning of the import chain. These tests run event picking over a random set of recently imported data to see if the data have been imported correctly, and can be accessed by both the CLI and the PanDA client. The second, the performance test, generates event lookup queries on sets of the EventIndex data and measures the response times. These tests enable studies of the response time dependence on the amount of requested data, and data sample type and size. Both types of tests run regularly on the existing system. The results of the regular tests as well as the statuses of the main EventIndex subsystems (services health, loaders status, filesystem usage, etc.) are sent to InfluxDB in JSON format via HTTP requests and are displayed on Grafana monitoring dashboards. In case (part of) the system misbehaves or becomes unresponsive, alarms are raised by the monitoring system

Abstract:

The ATLAS experiment is preparing a major change in the conditions data infrastructure in view of LHC Run 4. In this paper we describe the ongoing changes in the database architecture which have been implemented for Run 3, and describe the motivations and the on-going developments for the deployment of a new system (called CREST for Conditions Representational State Transfer, as a reference to REST architectures). The main goal is to set up a parallel infrastructure for full scale testing before the end of Run 3