High Energy Experiment-Dept of Physics - Carnegie Mellon University

Experimental High Energy Particle Physics

Faculty: Roy Briere
Richard Edelstein (Emeritus)
Arnold Engler (Emeritus)
Thomas Ferguson
Robert Kraemer (Emeritus)
Manfred Paulini
James Russ
Helmut Vogel

Group Overview

High energy particle physics (HEP) studies the fundamental interactions of elementary particles, among them the six quarks and six leptons of the standard model of particle physics. Many of our activities focus on the physics of heavy quarks, especially the bottom (b) quark and the charm (c) quark. These are "cousins" of the up and down quarks that bind to form the familiar proton and neutron. Several mysteries in the very successful standard model of particle physics involve the weak interaction, which can be studied via the decays of these heavy quarks. Among these mysteries are the matter-antimatter asymmetry of the universe and the origin of mass. We are also interested in new physics beyond the standard model searching for the production of dark matter particles in particle collisions.

Our faculty currently work on the energy frontier with the CMS experiment at the large Hadron Collider (LHC) near Geneva, Switzerland, and on precision charm physics with the  BESIII experiment at IHEP in Beijing, China as well as the Be experiment at KEK in Japan. We are also still involved in the CDF experiment at Fermilab near Chicago, Illinois. Our group is active in various aspects of our collaborations, playing significant roles in detector construction, software infrastructure, physics analysis, and collaboration management. Recently, members of the CMU HEP group have been involved in the first observation of Bs meson oscillations, precision measurements of weak charm decays, construction of the CMS experiment at the LHC as well as CMS data analyses.

Our HEP group also has ties to many other groups in our Department. The High Energy Theory group has been very active in weak-interaction topics relevant to heavy-quark physics. Our collaborations have made many contributions to hadron spectroscopy (finding new bound states of quarks), which overlap with some of the efforts in our Medium Energy Experiment group. Furthermore, lattice QCD and other techniques of the Medium Energy Theory group are important to both weak physics and hadronic spectroscopy. Finally, the energy-frontier work at the LHC has the potential to discover specific new particles that may form the dark matter of the universe, a major interest of the McWilliams Center for Cosmology.

Member Research Thrusts

Briere studies heavy quarks produced at electron-positron colliders. Current efforts include ongoing work with the BESIII  detector in Beijing, and preparations for data-taking with BelleII in Japan. The main physics thrust is weak decay "flavor physics" based on decays of D and B mesons, which contain the heavy quark types (flavors) charm and bottom, respectively.  Their decays allow studies of CP violation and other rare phenomena used to search for hints of new physics. His other contributions to experiments include drift-chamber calibration and simulation, analysis tools, and various management roles.

Ferguson's research interests are in experimental high-energy particle physics and, in particular, the use of electron-positron and proton-proton colliding beam accelerators. A member of the Compact Muon Solenoid (CMS) collaboration, which has constructed a massive detector for the Large Hadron Collider (LHC). The LHC is a 14 TeV proton-proton colliding beam accelerator, situated at the European accelerator center, CERN, in Geneva, Switzerland. Since beginning to run in 2010, the LHC has reached 8 TeV in center-of-mass energy and is already close to its design intensity.  The best-known result from the LHC so far is the discovery of the Standard Model Higgs boson in 2012 by the CMS and ATLAS experiments. In the future, we hope to discover entirely new families of particles beyond the Standard Model, such as supersymmetry.

Paulini studies questions connecting particle physics phenomena to issues relevant to cosmology. One of those questions concerns the fact that our visible universe exhibits a predominance of matter over antimatter. A process in particle physics called CP violation is considered relevant for breaking the symmetry between matter and anti-matter particles. Paulini has studied CP violation in mesons containing b-quarks with the CDF experiment at Fermilab. Another question concerns the nature of dark matter that makes up about one quarter of the content of the universe. Paulini currently searches for the production of dark matter particles with the CMS experiment at CERN. He is in particular interested in supersymmetric models involving the decay of dark matter particles to photons in the final state.

Russ's research centers on heavy quark physics at CDF and CMS, as well as particle astrophysics studies of ultra-high energy neutrino sources, e.g., Active Galactic Nuclei. At CDF Russ is involve in B-physics and Quarkonium studies. These lead naturally into similar physics studies in the early running at CMS. Later Russ will work on Exotic searches for New Physics, using muons as probes. The neutrino work is now at the prototype stage and will develop over the next several years.

Vogel's research interests are in experimental high-energy physics at colliding-beam accelerators, most recently the proton-proton collider, LHC, at CERN, whose center-of-mass energy of 8 TeV is the highest ever achieved. There, the CMS and ATLAS experiments have recently discovered a Higgs boson to complete the Standard Model of the unified electroweak interaction. At the LHC Vogel is involved in the CMS experiment. His main interests are studies of heavy quarkonium (charmonium and bottomonium) and searches for physics beyond the Standard Model in the form of additional quarks beyond the known three families.