Jets in Photoproduction and in the Transition Region to DIS at the HERA Collider

Recent results on jets in photoproduction and in deep-inelastic scattering at low $Q^2$ by the H1 and ZEUS collaborations are reviewed.Comment: 4 pages, 5 figures. To appear in the proceedings of 32nd International Conference on High-Energy Physics (ICHEP 04), Beijing, China, 16-22 Aug 200

Istraživanja ep sudara na najvišim Q2 I P_T sudaračem HERA

The HERA collider with its center of mass energy of 318 GeV makes it possible to study a wide range of electroweak physics as well as to search for physics beyond the Standard Model (SM). In this article, recent results, obtained by the two collider experiments H1 and ZEUS, are reviewed. The cross sections for inclusive neutral current and charged current processes are shown, and results from a combined electroweak and QCD analysis of the data are discussed. Selected results from searches for physics beyond the SM are presented.Sudaračem HERA, na energijama u sustavu središta mase od 318 GeV, može se proučavati široko područje elektroslabe fizike, kao i tražiti pojave izvan standardnog modela (SM). Izlažemo pregled nedavnih ishoda dvaju mjerenja sudara, H1 i ZEUS. Prikazujemo udarne presjeke inkluzivnih procesa neutralnih i nabijenih struja, te raspravljamo ishode skupnih elektroslabih i QCD analiza. Predstavljamo i ishode traganja pojava izvan SM-a

Performance of a Modular Ton-Scale Pixel-Readout Liquid Argon Time Projection Chamber

The Module-0 Demonstrator is a single-phase 600 kg liquid argon time projection chamber operated as a prototype for the DUNE liquid argon near detector. Based on the ArgonCube design concept, Module-0 features a novel 80k-channel pixelated charge readout and advanced high-coverage photon detection system. In this paper, we present an analysis of an eight-day data set consisting of 25 million cosmic ray events collected in the spring of 2021. We use this sample to demonstrate the imaging performance of the charge and light readout systems as well as the signal correlations between the two. We also report argon purity and detector uniformity measurements and provide comparisons to detector simulations

Search for light long-lived neutral particles that decay to collimated pairs of leptons or light hadrons in pp collisions at √s = 13 TeV with the ATLAS detector

A search for light long-lived neutral particles with masses in the O(MeV-GeV) range is presented. The analysis targets the production of long-lived dark photons in the decay of a Higgs boson produced via gluon-gluon fusion or in association with a W boson. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are selected in 139 fb−1 of √s = 13 TeV pp collision data collected by the ATLAS detector at the LHC. Background estimates for contributions from Standard Model processes and instrumental effects are extracted from data. The observed event yields are consistent with the expected background. Exclusion limits are reported on the production cross-section times branching fraction as a function of the mean proper decay length cτ of the dark photon, or as a function of the dark-photon mass and kinetic mixing parameter that quantifies the coupling between the Standard Model and potential hidden (dark) sectors. A Higgs boson branching fraction above 1% is excluded at 95% CL for a Higgs boson decaying into two dark photons for dark-photon mean proper decay lengths between 10 mm and 250 mm and dark photons with masses between 0.4 GeV and 2 GeV

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)

Search for pair production of boosted Higgs bosons via vector-boson fusion in the bb¯bb¯ final state using pp collisions at √s=13 TeV with the ATLAS detector

A search for Higgs boson pair production via vector-boson fusion is performed in the Lorentz-boosted regime, where a Higgs boson candidate is reconstructed as a single large-radius jet, using 140 fb−1 of proton-proton collision data at s√=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Only Higgs boson decays into bottom quark pairs are considered. The search is particularly sensitive to the quartic coupling between two vector bosons and two Higgs bosons relative to its Standard Model prediction, κ2V. This study constrains κ2V to 0.55<κ2V<1.49 at 95% confidence level. The value κ2V=0 is excluded with a significance of 3.8 standard deviations with other Higgs boson couplings fixed to their Standard Model values. A search for new heavy spin-0 resonances that would mediate Higgs boson pair production via vector-boson fusion is carried out in the mass range of 1-5 TeV for the first time under several model and decay-width assumptions. No significant deviation from the Standard Model hypothesis is observed and exclusion limits at 95% confidence level are derived