The ATLAS experiment is preparing for data taking at 14 TeV collision energy. A rich discovery physics program is being prepared in addition to the detailed study of Standard Model processes which will be produced in abundance. The ATLAS multi-level trigger system is designed to accept one event in 2 • 10B to enable the selection of rare and unusual physics events. The ATLAS calorimeter system is a precise instrument, which includes liquid Argon electromagnetic and hadronic components as well as a scintillator-tile hadronic calorimeter. All these components are used in the various levels of the trigger system. A wide physics coverage is ensured by inclusively selecting events with candidate electrons, photons, taus, jets or those with large missing transverse energy. The commissioning of the trigger system is being performed with cosmic ray events and by replaying simulated Monte Carlo events through the trigger and data acquisition system.

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Landslides commonly occur on earth's surface, in a wide range from subaerial landscapes to submarine oceanic regions. These events can trigger the generation of hazardous tsunamis that can have major consequences such as overtopping of dams and reservoirs, and coastal flooding and erosion. Globally, tsunamis have caused more than 250,000 fatalities over the past 30 years, triggered by landslides, earthquakes, and other sources combined (Gusiakov et al., 2019), and for this reason they are one of the primary natural hazards to coastal communities and infrastructure. The triggering conditions of tsunamis are often associated with large surface deformations caused by seismic events (

Submerged mass flows are commonly considered a natural geohazard that interacts with terrestrial and submarine infrastructure and communities and are linked to the generation of tsunamis. Previous studies have investigated submerged mass flows by means of the benchmark case of a granular column collapse. This study explores the mobility and collapse dynamics of submerged granular columns within a planar configuration as a function of the column aspect ratio a. The use of a planar configuration allows the monitoring of the moving mass and its deformation patterns and provides a novel insight into the particle-fluid interactions at release and during collapse not possible before. Special attention was devoted to the column saturation and release mechanism. The column mobility is observed to be directly controlled by a and is linked to a clear distinction between triangular and trapezoidal deposits. The column collapse is found to be described by two characteristic times, marking transition points through the collapse stages. The associated deformation patterns reflect both at a column scale and at localized particle groups during collapse, reflecting in the velocity scaling of a deformable and moving granular mass and the occasional ejection of particles at its surface. We observed that the area of the released portion decreases during collapse and converge toward an equivalent portion of surface particles with little influence by a. The experimental results provide a novel insight into the study of submerged mass flows and set a reference behavior for future numerical validations.

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The DAQ/HLT system of the ATLAS experiment at CERN, Switzerland, is being commissioned for first collisions in 2009. Presently, the system is composed of an already very large farm of computers that accounts for about one-third of its final event processing capacity. Event selection is conducted in two steps after the hardware-based Level-1 Trigger: a Level-2 Trigger processes detector data based on regions of interest (RoI) and an Event Filter operates on the full event data assembled by the Event Building system. The detector read out is fully commissioned and can be operated at its full design capacity. This places the responsibility on the High-Level Triggers system to select only events of highest physics interest that will finally reach the offline reconstruction farms. This paper brings an overview of the current ATLAS DAQ/HLT implementation and performance based on studies originated from its operation with simulated, cosmic particles and first-beam data. Its built-in event processing parallelism is presented and discussed.