Experimental Particle Physics Research Group

ATLAS

ATLAS is one of the two multi-purpose experiments taking data at CERN’s Large Hadron Collider (LHC), near Geneva in Switzerland. The LHC recreates conditions thought to have existed in our Universe shortly after the Big Bang. Beams of protons (or, sometimes, heavy ions) are accelerated to very high energies around the 27-km LHC tunnel, located approximately 100 m underground. The beams are then crashed together in heads-on collisions at specific intersection points around the accelerator, where sophisticated detectors such as ATLAS are used to study the debris from the beam collisions. The first period of LHC running (Run-1) concluded in 2012, having collected more than 20 fb-1 worth of proton-proton data, at centre-of-mass energies of up to 8 TeV and peak instantaneous luminosities of 7×1033cm-2s-1. The analysis of LHC data has already led to major advances in our understanding of fundamental particle interactions, most notably with the breakthrough discovery of the Higgs boson in July 2012. 

Building on the successes of Run-1, and while continuing to study Higgs boson properties and other Standard Model processes with high precision, particle physicists from all over the world, including the Sussex ATLAS team, are now focusing much of their efforts on the search for manifestations of new physics phenomena at the LHC. LHC operations are resuming in 2015 for the beginning of Run-2, when the accelerator will be running at centre-of-mass energies of 13 TeV and expected instantaneous luminosities as high as 1.6×1034cm-2s-1. By the end of Run-2, ATLAS will have collect approximately 30 fb-1 worth of proton-proton data.

A staged programme of both machine and detector upgrades is foreseen for the next decades at the LHC. These will enable ATLAS to collect order of 300 fb-1 of proton-proton collisions at 14 TeV by the middle of the next decade (Phase-1 upgrade; instantaneous luminosity: 2-3×1034cm-2s-1), and order of 3,000 fb-1 worth of data by approximately 2035 (Phase-2, or HL-LHC, upgrade; instantaneous luminosity: 6-7×1034cm-2s-1).

The Sussex ATLAS team, led by Professor Antonella De Santo, counts four other faculty members: Dr Lily Asquith (a Dorothy Hodgkin Royal Society fellow), Dr Alessandro Cerri, Dr Fabrizio Salvatore, and Dr Iacopo Vivarelli. The group also has six post-doctoral researchers, five PhD students, and ten Masters-level project students. Sussex makes leading contributions to the ATLAS physics programme, with focus on supersymmetry searches, flavour physics, jet sub-structure physics, and Higgs physics. We coordinate a number of physics analysis groups at ATLAS: the SUSY Electroweak group; the SUSY Third Generation group; the SUSY Strong Production with Taus group; the SUSY 3-lepton group; and the Jet Sub-structure group. Sussex researchers are also involved in the study of parton density functions and in top-quark physics measurements. The ATLAS Deputy Run Coordinator is from Sussex and we hold key responsibilities in the experiment’s overall operations. We make major contributions to the ATLAS trigger system, with focus on core software for the ATLAS High-Level Trigger (HLT), a well as on trigger inner detector tracking, trigger operations, and trigger performance studies. We also work on the development of the trigger system in view of future high-luminosity LHC upgrades. We focus on the HLT Phase-1 upgrade and make major contributors to the design of a Level-1 tracking trigger system (L1Track), proposed for the HL-LHC upgrade phase.