The ATLAS (A Toroidal LHC ApparatuS) experiment at CERN near Geneva has been in operation since 2009, studying proton-proton collisions at the highest energies ever achieved in the laboratory. ATLAS is a general purpose experiment that searches for a wide variety of phenomena, and was one of two detectors at CERN to discover the Higgs particle. This discovery confirmed the mechanism by which fundamental particles have mass in the Standard Model of particle physics. In addition to refining Higgs boson measurements, ATLAS is now used to search for Beyond Standard Model (BSM) physics, including supersymmetry (susy), extra dimensions, dark matter and quark substructure.

The ATLAS collaboration involves many institutions worldwide, each of which tend to specialize in a few of the many physics searches being undertaken. Our group is currently focused on Higgs boson measurements in di-tau and WW final states, searches for physics beyond the standard model and quark substructure. The group is strongly involved with general ATLAS computing and ATLAS detector upgrades. The proposal for the Tier-1 data centre at TRIUMF was led by SFU, and the University is hosting a Tier-2 data centre which will provide a data access gateway. Our group is also contributing to several aspects of the ATLAS detector upgrades. For the new ATLAS Inner Tracking detector (ITk), SFU is building ITk silicon-microstrip modules and is developing fully automated ITk module mounting onto the larger ITk detector structures (petals) at TRIUMF.

ATLAS detector upgrades

SFU is active in testing and building new components of ATLAS to maintain and enhance the discovery potential of the experiment during the scheduled LHC operation at much higher collision rates during the High-Luminosity LHC.

New Muon ATLAS New Small Wheel (NSW). The Canadian Foundation for Innovation has  supported a consortium from Carleton, McGill, SFU and TRIUMF to replace the present first muon detector station of ATLAS in the forward regions with the so-called New Small Wheels (NSWs). The NSWs are fast, high precision muon tracking detectors with a diameter of approximately 9m (“small” compared to the ATLAS Big Wheels that span about 22m). SFU researchers, together with collaborators from Canada and Israel have successfully tested the first full sized prototype NSW chambers at a beam test experiment at Fermilab in 2014.

Test of the first full size small-strip thin gap chamber (sTGC) for the ATLAS New Small Wheel detector tested by Israeli and Canadian collaborators (SFU, Carleton and Montreal) at Fermilab in 2014.

New ATLAS Inner Tracker (ITk). The current ATLAS inner tracking detector will have to be replaced. The design of the ITk, is based on high granularity radiation hard silicon-strip and pixels with a total active area of about 180 m2, arranged in pixel and strip barrel layers and six endcap discs. The Canadian Foundation for Innovation has supported a consortium from Toronto, SFU, Carleton, Montreal, York and TRIUMF to contribute about 2 ½ disks for the ITk endcap strip-detector system by 2024. SFU is building about 500 ITk silicon-microstrip modules using infrastructure the group has setup at 4D Labs and is developing fully automated ITk module mounting onto the larger ITk detector structures (petals) at TRIUMF.

The new ATLAS Inner Tracker (ITk) will have a total active area of about 180 m2, arranged in pixel and strip barrel layers and six endcap discs.

Current ATLAS detector impressions:

DØ at Fermilab

The DØ experiment at Fermilab near Chicago operated from 1992 to 2011, studying proton-proton collisions just like ATLAS does currently. Our group’s activities on DØ focussed on top-quark physics, calorimetry, and computing. In particular we contributed to the first observation of electroweak top quark production, also known as “single top production”. Top quarks had previously only been seen to be produced in pairs via the strong interaction, and the discovery of single top production provided a key insight. The three central contributors to this discovery were honoured for this work, with Dugan O’Neil awarded the BC Innovation Council’s Young Innovator prize, Yann Coadou (research associate) awarded the Fermilab Tollestrup Award, and Dag Gilberg (graduate student) selected to give a plenary talk at the Fermilab Users’ Meeting.

CDF at Fermilab

Faculty member Bernd Stelzer provided our group’s connection to the CDF (Collider Detector at Fermilab) experiment, which ran from 1985 to 2011. Bernd was involved with several key CDF analyses, including Higgs boson searches, the first observation of single top quarks and BSM searches. Bernd led the CDF single top discovery group from 2007 to 2010.