Columbia is home to two experimental particle physics groups that aim to test the Standard Model of particle physics, and seek new physics beyond this model:

Columbia ATLAS Group

ATLAS is an experiment operating at the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. The LHC is the world's highest energy accelerator, and will be the premier experimental HEP collider facility for the energy frontier for many years to come.

The foremost question of HEP is the source of so-called "electroweak symmetry breaking" (EWSB), related to the issue of the origin of mass. The Standard Model (SM) of particle physics postulates the existence of the Higgs boson to solve this issue. In July 2012, ATLAS and CMS, the two large LHC experiments, announced the discovery of a new particle with properties very much like those predicted for the Higgs boson. As a result, the 2013 Nobel Prize in Physics was awarded to Peter Higgs and Francois Englert, two of the theorists who, in 1964, proposed this solution for EWSB. Whether this new particle behaves precisely as expected for the Higgs boson, or whether there are discrepancies that could point the way to new physics, is an area of intensive study. In addition, even with the Higgs boson, there are many questions that cannot be answered by the SM. Many other scenarios (eg. supersymmetry, technicolor, even the existence of extra spacetime dimensions) have been proposed. The LHC and ATLAS are designed to explore in detail physics at the TeV scale, where it is widely expected that signs of new physics should be discoverable.

The Columbia ATLAS Group has played a number of roles in the ATLAS experiment, including leading the development (from design through installation and commissioning) of the readout electronics of the liquid argon calorimeters for the ATLAS detector. The group has been heavily involved in physics analysis with the enormous data samples recorded in Run 1 at the LHC (2010-2012) at proton-proton center-of-mass energies of 7 TeV and 8 TeV, and more recently in Run 2 (2015-2018) at 13 TeV. In addition, the group is performing R&D aimed at developing the next generation of readout electronics for the ATLAS calorimeter system.

Students and researchers in the Columbia ATLAS Group are based at either Nevis Labs in New York, or CERN in Geneva Switzerland. Students have the opportunity to work on physics analysis, including searches for new physics with the 13 TeV data from the LHC Run 2, and also to be involved in the R&D on development of readout electronics for the HL-LHC upgrade of the ATLAS liquid argon calorimeter system.

Contact PIs: Gustaaf Brooijmans, John Parsons and Mike Tuts

Columbia Neutrino Group

The Columbia Neutrino Group is involved in a number of accelerator-based neutrino experiments that share the same detector technology, that of a liquid argon time projection chamber (LArTPC), as well as the IceCube-Gen2Coherent Captain Mills, and IsoDAR experiments. All of these experiments share the common physics mission of searching for new physics in the neutrino sector.

MicroBooNE is a LArTPC neutrino experiment at Fermilab, and the first large-scale LArTPC experiment to be constructed in the US. It has been collecting data since 2015 and is investigating neutrino properties and interactions using the Fermilab Booster Neutrino Beam. One of its primary physics goals is to perform a follow-up investigation of the unexplained excess of electron-like events in the MiniBooNE experiment. Since MiniBooNE is a short-baseline experiment, one of the leading interpretations of this excess is short-baseline neutrino oscillations which would be due to the presence of additional, sterile neutrino states associated with neutrino masses at ~1 eV. Other interpretations involve single-photon-inducing neutrino interactions, which, in MiniBooNE, were an irreducible background. In either case, the anomalous MiniBooNE signal may be from some type of new physics either within or beyond the Standard Model.

Beyond searches for new physics, MicroBooNE will provide improved measurements of several neutrino cross sections relevant for current and future neutrino experiments. It will also be a test setup for future very large (~10-100 kton) liquid argon detectors, such as the future Deep Underground Neutrino Experiment (DUNE), whose goals include the discovery of CP violation in the neutrino sector, the determination of the neutrino mass hierarchy, searches for proton decay and other baryon-number-violating processes, and searches for neutrinos from galactic supernova bursts.  

The Columbia Neutrino Group have led the design and construction of the readout electronics for the MicroBooNE detector. They are leading the same effort on the up and coming Short Baseline Near Detector (SBND), which is part of the Fermilab Short Baseline Neutrino (SBN) experimental program. These readout systems also provide a platform for trigger and data acquisition development toward DUNE, which are critical for DUNE's physics mission. The group is also involved in developing pattern recognition techniques and reconstruction tools for all of these experiments as well as procedures to distinguish between neutrino interactions and background events and between electrons and photons. Part of this involves applying “deep learning” convolutional neural net techniques. The group is also exploring similar techniques involving machine learning for implementation in the readout and trigger systems of SBND and DUNE.

On the physics side, the Columbia Neutrino Group has a long history in short-baseline neutrino physics and related neutrino phenomenology. The group is leading several analyses on MicroBooNE and SBN, including the follow-up investigation of the MiniBooNE low energy excess, and searches for sterile neutrino oscillations with SBN. Columbia Neutrino students and researchers are based at either Nevis Labs or at Fermilab, and are involved in both physics analysis and hardware development efforts. 

Contact PIs: Georgia Karagiorgi and Mike Shaevitz