ATLAS detector - schematic view

ATLAS detector - schematic view

Ph.D Research with the Birmingham ATLAS group

Staff: Phil Allport, Juraj Bracinik, Dave Charlton, Andrew Chisholm, Laura Gonella, Francesco Gonnella, Chris Hawkes, Stephen Hillier, Jacob Kempster, Ioannis Kopsalis, Paul Newman, Kostas Nikolopoulos, Rhys Owen, Mark Slater, Richard Staley, Juergen Thomas, Paul Thompson, Alan Watson, Miriam Watson, Steve Worm

Students: Daniel Briglin, James Broughton, Andrew Foster, Patrick Freeman, Nandish Gorasia, James Kendrick, Daniel Lewis, Jack Lindon, Rhys Owen, Elliot Reynolds, Russell Turner, Robert Vallance, Govind Virdee

The "Standard Model" of electroweak interactions requires additional physics to break the symmetry between the weak and electromagnetic interactions, generating the masses of the W and Z gauge bosons. The favoured candidate for this is the Higgs mechanism, which predicts the existence of one or more "Higgs bosons". The Large Hadron Collider (LHC) is being built to investigate the physics of electroweak symmetry breaking, establishing or refuting the existence of the Higgs bosons, and also to search for other new physical phenomena which may appear on the same energy scale (approximately 100 GeV to 1 TeV). One such candidate, supersymmetry, predicts a plethora of new particles within the reach of ATLAS and the LHC. ATLAS is one of the two general-purpose detectors that record proton-proton collisions at the LHC.

In July 2012, the experiments at the LHC confirmed the existence of a particle consistent with the predicted Higgs particle with a mass of around 125 GeV/c^2 (see: CERN Press Release). The focus is now on measuring and confirming in detail the properties of this particle, while the search for new physics continues, namely supersymmetric particles and possible further higher-mass Higgs bosons.

A wealth of different physics will be accessible at the LHC. We are currently involved in studies of the Higgs boson, studies of top quark production and other heavy quark flavours, and diffractive physics. It would be most natural for students to work in these areas, although we constantly review our programme as the data-taking and analysis progress. We are also involved in understanding the performance of the ATLAS trigger and semiconductor tracker, and planning for future upgrades of the ATLAS detector.

Part of the L1Calo system at the ATLAS electronics hall

Part of the first-level calorimeter trigger system at the ATLAS electronics hall
At the end of the 2012 proton=-proton run, after three years of data-taking, ATLAS has recorded more than 20 fb-1 of data at a 8 TeV centre of mass energy, achieving the most optimistic projections from the start of the year. This abundance of data will allow a wide range of precision and search physics over the next two years. After extensive work to update the collider and experiments for the 13 TeV centre of mass energy, data-taking has restarted in spring 2015, and the amount of collected data is already surpassing expectations.

The Birmingham group has made major contributions to the design, construction and operation of the ATLAS experiment and its associated software. Our main hardware responsibility is now on the operation and optimisation of the first-level calorimeter trigger of ATLAS, which we built with five other UK and international partner institutes. The first-level calorimeter trigger is implemented in fast electronics, applying a "pipeline" concept so that the signals from many beam-crossings are flowing through the system at once. This system provides the essential first level of triggering of the detector on electrons, photons, taus, hadronic jets and the possible presence of unidentified particles via missing energy - i.e. all the essential trigger signatures except for muons.

We were also an important contributor to the construction and testing of the ATLAS semiconductor tracker (SCT). As LHC energy and luminosity increase, both trigger and tracker will face an increasingly challenging environment. We are currently studying and designing future upgrades to the trigger system and preparing for construction of an upgraded tracker, and there will be opportunities for students with an interest in the hardware to work on these projects.

Our group is currently involved in the assembly and testing of prototypes of a new generation of semiconductor tracker modules, which will soon turn into preparations for the production of the new Inner Tracker (ITk) for ATLAS planned for installation around 2024. The production will take place in our new purpose-build clean room which opened in 2016, the Birmingham Instrumentation Laboratory for Particle physics and Applications (BILPA). We perform tests of prototype chips and modules, as well as silicon sensors, to ensure their suitability and reliability in this complex and large system. The group also works on physics performance studies for the high-luminosity LHC, and participates in testbeam activities at both CERN and DESY.

Wire-bonding

Ultrasonic wire-bonding makes the electrical connections on SCT readout hybrid circuits

The UK particle physics community is a strong supporter of the latest e-science initiative to build a next generation internet - the grid - using advanced distributed computing techniques. Here in Birmingham we are part of a "Tier-2" computing centre on the Grid, together with other institutes in the south of England. We additionally have significant local computing facilities for ATLAS physics analysis.

We would normally anticipate that in addition to physics studies/data analysis, students also participate in work in one of our hardware or software activities, giving a balance of experience. All of the topics involve interaction with other groups within and beyond the UK, and require working visits to CERN. It would also be natural for students to spend extended periods of time at CERN when the experiment is operating.

Further information about ATLAS