High Energy Physics Theory

Overview

The experimental particle physics group at UVA is currently making major contributions to the CMS, NOvA, Mu2e, and LDMX experiments:
CMS
The Compact Muon Solenoid (CMS) experiment is one of two large general-purpose particle physics detectors built on the Large Hadron Collider (LHC) at CERN in Switzerland and France. The goal of CMS experiment is to investigate a wide range of physics, including the search for the Higgs boson , extra dimension , and particles that could make up dark matter . The CMS group (Cox, Hirosky, Neu) has a wide range of physics interests, including Higgs boson and top quark studies, standard model measurements, and searches for supersymmetric particles and other exotic forms of matter. Our detector efforts have focused on the CMS electromagnetic and hadronic calorimeters and we are currently leading upgrade efforts for the CMS calorimeters and for a new dedicated precision timing detector for charged particle tracks in the High-Luminosity LHC era.
NOvA
The NOvA (NuMI Off-axis ν Appearance) experiment is shedding light on one of nature's most elusive particles: neutrinos. Since the late 1990s, physicists have known that neutrinos exhibit a quantum mechanical behavior called oscillations. But this behavior is not predicted by the Standard Model of particle physics. NOvA is working to better understand these strange particles through precision measurements of their oscillation properties. The UVA group lead the effort to design and fabricate the NOvA Power Distribution System and is actively involved in physics analysis for this ongoing and world-leading neutrino experiment.
Mu2e
The Mu2e experiment will search for new physics through lepton-number violation: that is, muons decaying into electrons without any associated neutrinos. This is an example of a relatively low-energy experiment probing energy scales unattainable by any existing or proposed accelerator-based collider experiment. UVA leads the effort to design and fabricate one of the three main detectors for Mu2e, the Cosmic Ray Veto. The ongoing fabrication is one of the largest undertakings ever by the High Energy Physics group at UVA.
LDMX
The constituents of dark matter are unknown, and the viable possibilities span a very large mass range. The region ~MeV to ~GeV is largely unexplored. If there is an interaction between this "light" dark matter and ordinary matter, then there necessarily is a production mechanism in accelerator-based experiments. The most sensitive way to search for this production is to use a primary electron beam to produce dark matter in fixed-target collisions. The Light Dark Matter eXperiment (LDMX) is a proposed experiment that has sensitivity to light DM in the sub-GeV range. In addition to the exciting possibility to detect and study the dark sector, the UVA group is interested in fabricating the hadronic veto calorimeter which plans to use a very similar technology as the Mu2e CRV which is currently being fabricated at UVA.


The Theoretical Elementary Particle Physics group acknowledges that the fundamental task of physics is to learn the rules of the basic interactions governing the behavior of matter and to search for new laws when present knowledge fails to answer the remaining mysteries of the observable universe. At the foundation of modern theories of particle physics is a deep and beautiful symmetry principle: the invariance of physical laws under symmetry transformations at every space-time point. Theories that show this symmetry are known as Yang-Mills or Gauge Theories. The Standard Model of Strong, Electromagnetic and Weak interactions is the most successful of these theories. It describes all known interactions of matter except gravity.
The Electroweak part of the Standard Model is being tested to a high degree of precision. The Strong interaction part, the Quantum Chromodynamics (QCD) Theory, which describes the interactions among the quarks, is being closely scrutinized, both perturbatively and nonperturbatively. The Standard Model is incomplete, however, since a number of fundamental puzzles, such as CP violation and the origin of masses, remain unsolved. The solutions to these problems probably lie outside the framework of the Standard Model. How does one solve the problem of masses? How does one solve QCD? These are among the topics under active investigation by UVa HEP theorists Hung and Thacker.

Personnel

Peter Arnold Peter Arnold
Ph.D., 1986, Stanford

Prof. Arnold studies the theory of the strong, weak, and electromagnetic interactions at extremely high, relativistic temperatures, such as in the very early Universe (less than a millionth of a second after the Big Bang) or in relativistic collisions in heavy ion accelerators. Topics he has studied include investigating why there is significantly more matter than anti-matter in the Universe and understanding the properties of quark-gluon plasmas. The theoretical methods used for these very high energy problems (as much as a quadrillion degrees Kelvin) can also be applied to certain ... More>

Pham Q. Hung Pham Q. Hung
Ph.D., 1978, UCLA

Elementary particle physics has been crowned with spectacular successes in this last quarter of the past century. The cornerstone of such a success is the Standard Model of Elementary Particles which has been tested to a high level of precision. The Standard Model (SM), however, is incomplete. It cannot predict the number of "families". (Experimentally, one knows that there at least three families.) It cannot predict the electroweak mixing angle which is measured to a high level of accuracy. One does not know the origin of the masses of the constituents of matter: the quarks ... More>

Diana Vaman Diana Vaman
Ph.D., 2001, SUNY, Stony Brook

My research in theoretical particle physics is based on string theory, and I am especially interested in the connections between gauge and string theories. More>

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