The MATHUSLA Test Stand

The rate of muons from LHC $pp$ collisions reaching the surface above the ATLAS interaction point is measured and compared with expected rates from decays of $W$ and $Z$ bosons and $b$- and $c$-quark jets. In addition, data collected during periods without beams circulating in the LHC provide a measurement of the background from cosmic ray inelastic backscattering that is compared to simulation predictions. Data were recorded during 2018 in a 2.5 $\times$ 2.5 $\times$ 6.5~$\rm{m}^3$ active volume MATHUSLA test stand detector unit consisting of two scintillator planes, one at the top and one at the bottom, which defined the trigger, and six layers of RPCs between them, grouped into three $(x,y)$-measuring layers separated by 1.74 m from each other. Triggers selecting both upward-going tracks and downward-going tracks were used.Comment: 18 pages, 11 figures, 1 tabl

The ATLAS Run-2 Trigger Menu for higher luminosities: Design, Performance and Operational Aspects

The ATLAS experiment aims at recording about 1 kHz of physics collisions, starting with an LHC design bunch crossing rate of 40 MHz. To reduce the massive background rate while maintaining a high selection efficiency for rare physics events (such as beyond the Standard Model physics), a two-level trigger system is used. Events are selected based on physics signatures such as presence of energetic leptons, photons, jets or large missing energy. The trigger system exploits topological information, as well as multi-variate methods to carry out the necessary physics filtering. In total, the ATLAS online selection consists of thousands of different individual triggers. A trigger menu is a compilation of these triggers which specifies the physics algorithms to be used during data taking and the bandwidth a given trigger is allocated. Trigger menus reflect not only the physics goals of the collaboration for a given run, but also take into consideration the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout and offline processing farm. For the 2017 run, the ATLAS trigger has been enhanced to be able to handle higher instantaneous luminosities (up to 2.0x10^{34}cm^{-2}s^{-1}) and to ensure the selection robustness against higher average multiple interactions per bunch crossing. In this presentation, we describe the design criteria for the trigger menus used for Run 2 at the LHC. We discuss several aspects of the process, from the fine-tuning of the prescales, the validation of the algorithms, and the monitoring tools that ensure the smooth operation of the trigger during data-taking. We also report on the physics performance of a few trigger algorithms

Searches for BSM physics using challenging and Long-Lived signatures with that ATLAS detector

Slides for a talk at ICNFP 202

The ATLAS Trigger Menu design for higher luminosities in Run 2

The ATLAS experiment aims at recording about 1 kHz of physics collisions, starting with an LHC design bunch crossing rate of 40 MHz. To reduce the large background rate while maintaining a high selection efficiency for rare physics events (such as beyond the Standard Model physics), a two-level trigger system is used. Events are selected based on physics signatures such as the presence of energetic leptons, photons, jets or large missing energy. The trigger system exploits topological information, as well as multivariate methods to carry out the necessary physics filtering for the many analyses that are pursued by the ATLAS community. In total, the ATLAS online selection consists of nearly two thousand individual triggers. A Trigger Menu is the compilation of these triggers, it specifies the physics selection algorithms to be used during data taking and the rate and bandwidth a given trigger is allocated. Trigger menus must reflect the physics goals of the collaboration for a given run, but also take into consideration the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout and offline processing farm. For the 2017 run, the ATLAS trigger has been enhanced to be able to handle higher instantaneous luminosities (up to 2.0x10^{34}cm^{-2}s^{-1}) and to ensure the selection robustness against higher average multiple interactions per bunch crossing. In this presentation we describe the design criteria for the trigger menu for Run 2. We discuss several aspects of the process of planning the trigger menu, starting from how ATLAS physics goals and the need for detector performance measurements enter the menu design, and how rate, bandwidth, and CPU constraints are folded in during the compilation of the menu. We present the tools that allow us to predict and optimize the trigger rates and CPU consumption for the anticipated LHC luminosities. We outline the online system that we implemented to monitor deviations from the individual trigger target rates and to quickly react to changing LHC conditions and data taking scenarios. Finally we give a glimpse of the 2017 Trigger Menu, allowing the listener to get a taste of the vast physics program that the trigger is supporting

Searches for R-Parity violating SUSY with lepton number violation

The violation of R-parity allows new signatures to be pursued in the search for supersymmetry at the LHC. This talk presents the latest results from the ATLAS experiment using 20/fb of pp LHC collision data of searches for R-parity violating SUSY scenarios with lepton number violation. The results presented are for dedicated searches for resonances, as well as a systematic analysis of the constraints placed on R-parity violating models with lepton flavour violation by the Run-1 ATLAS searches, including those which were originally developed to target R-parity conserving models

Searches for new physics with unconventional signatures at ATLAS and CMS

Summary of the latest results on searches for BSM with unconventional signatures in ATLAS and CM

The ATLAS trigger menu: from Run 2 to Run 3

The ATLAS experiment aims to record about 1 kHz of physics collisions. This is achieved by using a two-level trigger system to select interesting physics events while reducing the data rate from the 40 MHz LHC crossing frequency. Events are selected based on physics signatures such as the presence of energetic leptons, photons, jets or large missing energy. The wide physics program carried out by ATLAS is achieved by running around 1000 triggers during data taking. A Trigger Menu is the compilation of these triggers, specifying the physics selection algorithms to be used during data taking and the rate and bandwidth a given trigger is allocated. Trigger menus must reflect the physics goals for a given run, and also must take into consideration the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout and offline processing farm. We will describe the design criteria for the ATLAS trigger menu. We discuss several aspects of the process of planning the trigger menu, including how rate, bandwidth, and CPU constraints are folded in during the compilation of the menu. Improvements made during the run to react to changing LHC conditions and data taking scenarios are discussed and we conclude with an outlook on how the trigger menu will evolve with the detector upgrades currently being installed for the start of Run 3

Searches for Exotic Phenomena at the LHC

Slides for PIC 2021, starting on 14 September in Aachen Material from ATLAS and CM

Supersymmetry searches in ATLAS

Weak scale supersymmetry remains one of the best motivated and studied Standard Model extensions. This talk summarises recent ATLAS results for searches for supersymmetric (SUSY) particles. Weak and strong production in both R-Parity conserving and R-Parity violating SUSY scenarios are considered. The searches involved final states including jets, missing transverse momentum, light leptons, taus or photons, as well as long-lived particle signatures

Search for BSM physics using challenging signatures with the ATLAS detector

Various theories beyond the Standard Model predict unique signatures which are difficult to reconstruct and for which estimating the background rates is also a challenge. Signatures from displaced decays anywhere from the inner detector to the muon spectrometer, as well as those of new particles with fractional or multiple value of the charge of the electron or high mass stable charged particles are all examples of experimentally demanding signatures. This review focuses on the most recent results using LHC pp collision data at 13 TeV collected by the ATLAS detector