Research Overview
The Sheffield ATLAS group is active in all aspects of the experiment, from design and construction, through commissioning and operation to analysis and interpretation of data. This work is funded by grants from STFC, HEFCE and the EU totalling more than £5M over the past 5 years.
Right from the start we have been involved in building the Semiconductor Tracker (SCT) detector situated at the heart of ATLAS. This detector allows the paths of charged particles produced in LHC collisions to be measured with high precision, enabling their momenta to be measured and the production of short-lived new particles to be identified. Much of our early work concentrated on testing large numbers of the high sensitivity Silicon detectors used in the SCT in order to guarantee that they would work when installed in ATLAS. Later on we worked alongside other UK groups to assemble and test the SCT Endcap-C detector and played a leading role in its installation into ATLAS. We also took the lead in modelling the background radiation environment in the experiment and studying its impact on detector operation and maintenance. Now our efforts concentrate on developing the complicated data acquisition (DAQ) software required to run the SCT and understanding its performance with the first data.
An increasingly important aspect of our work is the development of software for processing and understanding the data produced by ATLAS. We are heavily involved in the development of software for reconstructing the properties of particles produced in ATLAS, in particular jets, electrons and photons (see also here). We are also responsible for the development of tools for identifying the locations of primary proton-proton collisions and decays of unstable particles and a member of the group co-coordinates the panel defining how the information from all ATLAS reconstruction software is passed to users for physics analysis (the ATLAS Event Data Model). We also co-coordinate the development of the software tools required to carry out this analysis.
The group is very active in the analysis of ATLAS physics data and, uniquely for a university group, has hosted three co-convenors of central ATLAS physics analysis Working Groups in the past five years: Craig Buttar (Standard Model 2004-2006), Dan Tovey (SUSY 2004-2006) and Davide Costanzo (SUSY 2006-2008). Our main interests lie in searches for the Higgs boson in the key 4-lepton and 2-photon channels and searches for dark matter particles predicted by Supersymmetry theory with jets and missing transverse energy. We are also active in studies of Minimum Bias events and the low energy interactions accompanying high energy proton-proton collisions (the Underlying Event). Understanding these processes will be crucial for modelling backgrounds to searches while also being interesting in their own right.
Analysis of the vast quantities of data produced each year by ATLAS can not be accomplished with a single desktop computer, or even with a single large supercomputer. Instead thousands of machines around the world must be utilised, connected via the internet to form a 'virtual' computer called the Grid. The group was a founder member of the GridPP collaboration coordinating particle physics Grid developments in the UK and secured a HEFCE SRIF2 grant in 2003 for its own computing cluster connected to the worldwide LHC Computing Grid (wLCG). This node forms a part of the local NorthGrid Tier-2 Grid node along with similar machines in Lancaster, Liverpool and Manchester. The Sheffield machine is now one of the most effective sites delivering data-processing to ATLAS. A member of the group is also a member of the small team of experts responsible for submitting simulation jobs to the Grid for the whole of ATLAS.
In the latter half of the next decade the Large Hadron Collider may be upgraded to deliver ten times the rate of collisions as is possible with the current design. To function at such high collision rates ATLAS will need to be modified substantially. We are currently carrying out R&D leading to the design of a new tracking detector to replace the SCT when it reaches the end of its useful life. Sheffield work focuses on modelling the expected increased radiation backgrounds, improving the design of the services supplying cooling and electrical power to the detector, and testing new radiation hard Silicon detectors.
Would you like to know more? Please contact Dan Tovey with any questions.
Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK
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