Physics

The ATLAS Experiment at SMU



What is ATLAS?

ATLAS stands for "A Toroidal LHC Apparatus" and is one of four major experiments located on the Large Hadron Collider (LHC). It is the largest particle physics detector ever constructed, standing eight stories tall, with a length half that of a U.S. football field, and weighing in at over 7000 tons. It is designed to take 40 million pictures per second of proton-proton collisions delivered by the LHC. These collisions recreate conditions in the universe about a billionth of a second after the universe came into being - an event known as "The Big Bang". By studying these collisions, we are learning about the laws of physics and the constituents of the universe just a tiny fraction of a second after it appeared. By doing so, we hope to learn about the fundamental structure of energy, matter, space, and time so that we can better understand the universe as it was, as it is now, and as it will be in the future.

SMU ATLAS Contributions

The SMU group has a strong history of making major contributions to the ATLAS experimental physics program, with areas of concentration including the search for, discovery of, and now measurement of the Higgs Boson; searches for additional Higgs Bosons in nature and for other signs of "beyond-the-Standard Model" (BSM) physics, such as supersymmetry, extra dimensions, magnetic monopoles, and other unique signatures of new phenomena. We have made and continue to make important technical and maintenance contributions to the experiment, including in the Liquid Argon (LAr) calorimeter system and the ATLAS trigger and data acquisition system (TDAQ).

We continue to serve the technical and physics analysis needs of the ATLAS Experiment providing opportunities for students and post-doctoral researchers to become engaged in leading questions in the field. The SMU ATLAS group believes in training the next generation of particle physicist through experience with developing skills in hardware and software, and tackling difficult problems that lie at the heart of modern physics. For more about our research interests, see the next section

Research on ATLAS

SMU graduate students and post-doctoral researchers, as well as research faculty and tenured or tenure-track faculty, all play important roles in our research efforts on ATLAS. To learn more, contact the four faculty members in the SMU ATLAS group:

  • Prof. Ryszard Stroynowski (Principal Investigator)
  • Prof. Robert Kehoe
  • Prof. Stephen Sekula
  • Prof. Jingbo Ye
You can find contact details on our Physics Department Personnel Webpage. Pictured right are some of our current graduate students, post-docs, and faculty in front of a small part of the vast ATLAS detector (taken in 2013).

Some of our most recent contributions to physics research with ATLAS have been:

  • Discovery of the Higgs Boson using H0 → ZZ(*) → 4 leptons, H0 → γ γ, and H0 → W+W-; we have also subsequently used these final states to understand the quantum numbers of the particle, and helped confirm its identity as a Higgs Boson. We have also searched for other Standard Model Higgs Boson decay modes, including H0 → Z0 γ

    "Observation of a New Particle in the Search for the Standard Model Higgs Boson with the ATLAS Detector at the LHC". ATLAS Collaboration. Phys.Lett. B716 (2012) 1-29.

    "Evidence for the spin-0 nature of the Higgs boson using ATLAS data." ATLAS Collaboration. arXiv:1307:1432. Submitted for publication.

    "Search for the Standard Model Higgs boson in the H → Zγ decay mode with pp collisions at √s = 7 and 8 TeV". ATLAS Collaboration. ATLAS-CONF-2013-009

  • Searches for additonal Higgs-like particles, including an electrically charged Higgs Boson, H+. Observation of an electrically charged scalar particle would be unambiguous evidence of BSM physics.

    "Search for charged Higgs bosons decaying via H+ -> taunu in top quark pair events using pp collision data at sqrt(s) = 7 TeV with the ATLAS detector." ATLAS Collaboration. JHEP 1206 (2012) 039

    "Search for charged Higgs bosons through the violation of lepton universality in ttbar events using pp collision data at sqrt(s) = 7 TeV with the ATLAS experiment". ATLAS Collaboration. JHEP03(2013)076.

  • Searches for di-photon resonances, which would be expected if there are extra spatial dimensions beyond the three already known dimensions; searches for magnetic monopoles, which if detected would explain the quantization of electric charge in nature.

    "Search for diphoton events with large missing transverse momentum with 1 fb-1 of 7 TeV proton-proton collision data with the ATLAS detector". ATLAS Collaboration. PLB 710 (2012) 519

    "Search for magnetic monopoles in sqrt(s) = 7 TeV pp collisions with the ATLAS detector". ATLAS Collaboration. PRL 109 (2012) 261803.

A complete list of ATLAS papers in which we are involved is to be found on our SMU Preprints Website.

Historical Picture of SMU on ATLAS

SMU physicists designed and built elements of readout electronics for the electromagnetic calorimeter system, including a 1600 channel optical link system with a total data rate of about 2.7 terabits per second. Before the turn-on of the experiment in 2009, most of our effort was devoted to the commissioning of the 220,000 detector channels and creation, validation, and deployment of control software. We have also been strongly involved in designing the software architecture to monitor the experiment in real-time.

The R&D program for the future detector upgrade is pursued together with the Electrical Engineering Department to develop very fast opto-electronics components that can work in a very high radiation environment.