Collider Physics

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The last piece in the puzzle, called the Standard Model of Particle Physics (SM), was put in place in 2012 with CERN's discovery of the Higgs boson.  This happened more than 50 years after its prediction. Is this triumph of the SM the end or just the begining of an even bigger puzzle where the missing pieces are still in the dark?

Around 1900 a great physicist said: There is nothing new to be discovered in physics now. All that remains is more and more precise measurement. And he could not have been more wrong: just a few years later both Quantum Mechanics and Relativity were discovered. Will nature be so kind to bestow another such surprise on us?

The role of Dark Matter and gravity in the quantum world could be key elements in this quest. The LHC allows us to shine light on the mysteries of the quantum world and test hypotheses of physics Beyond the Standard Model (BSM), such as Supersymmetry or the existence of Extra Spatial Dimensions. With a bit of luck we might see hints of what could be described as an even bigger puzzle of which the SM is just the first piece.


The ATLAS group of the DPNC is heavily involved in all areas of the experiment:

  • Hardware: construction of a new silicon tracker for HL-LHC (tracker layout, mechanics, novel HV-CMOS monolithic silicon detectors, Level-1 track trigger)
  • Data analysis: searches for physics beyond the SM with focus on high-pT objects including jets, boosted objects, b-jets, and MET
  • Novel techniques for data reconstruction: b-tagging, boosted object-tagging, particle flow
  • Machine Learning: applications to open HEP questions such as CPU-limitation in Run-4 tracking and fast calorimeter shower simulation, improvements to b-tagging and boosted object-tagging


The UNIGE ATLAS group has a large track record of past contributions:

  • Hardware: construction of the current ATLAS detector: strip tracker, trigger/DAQ, calorimeter readout electronics, SC toroid coil casings, and the IBL (Inner Barrel Layer)
  • Data analysis: Higgs discovery, SM measurements, searches for physics beyond the SM
  • Major responsbilities held by UniGe ATLAS members include: technical coordination; silicon tracker coordination (SCT + IBL); trigger/DAQ construction, operation and coordination; publications; analysis coordination; detector alignment; and detector upgrade.

A short history of the LHC era:

the LHC started producing proton-proton collisions at the centre of the ATLAS experiment in 2010 at a centre-of-mass energy of 7 TeV, increasing this value to 8 TeV in 2012, leading to the Higgs-boson discovery. After a two-year shutdown the energy was increased to 13 TeV. Since 2015 the LHC is running with this energy, pushing the search for BSM physics to higher and higher masses, lower cross sections and larger lifetime. The multi-purpose nature of the ATLAS detector allows this search program to grow steadily in breadth and depth. In addition the Higgs boson and its properties are studied in great detail as the luminosity increases, as are other SM properties.

Looking ahead, by the end of 2023 a ten-fold increase in the luminosity of the 13 TeV data set is expected as compared to the end of 2016. After another shutdown where both ATLAS and the LHC are upgraded, the so-called High-Luminosity LHC phase starts in 2026 until 2035, in which the luminosity will be increased by another order of magnitude, both pushing the sensitivity to direct new physics discovery and precision Higgs and SM measurements to unprecedented areas.

Département de Physique Nucléaire et Corpusculaire | 2017 | Impressum.