Faculty :
Lay Nam Chang;
Patrick Huber;
Djordje Minic;
Tetsuro Mizutani;
Eric Sharpe;
Tatsu Takeuchi
Emeriti Faculty:
Dick Arndt;
Chia Tze
Research Associates:
Robert Karp
What is matter?
Will it last forever?
The Teacher answered:
All that is born, all that is created,
all the elements of nature
are interwoven and united with each other.
All that is composed shall be decomposed;
everything returns to its roots;
matter returns to the origins of matter...
from "The Gospel of Mary Magdalene", translated from Coptic to French by Jean-Yves Leloup, translated from French to English by Joseph Rowe. ISBN:0-8928-1911-1.
The Theoretical Particle Physics & String Theory group at Virginia Tech
is working on a wide range of problems addressing the fundamental nature of the
universe and its constituents.
Our current knowledge of elementary particles and their interactions can be summarized in the chart shown here.
There exist 6 flavors of quarks (u, d, s, c, b, t, in the order of discovery) and 6 flavors of leptons (e, μ, νe, νμ, τ, ντ, again in the order of discovery) which interact with each other through the exchange of the force carrier particles. All the quarks couple to γ (photon), g (gluon), Z, and W, while the charged leptons (e, μ, and τ) couple to γ, Z, and W, and the neutrinos (νe. νμ, and ντ) only couple to the Z and the W.
Huber has studied the potential offered by a number of proposed new neutrino experiments to discover a non-zero mixing angle
θ13 and to explore leptonic CP violation. The
focus of his research was on numerical methods to accurately and
efficiently predict physics sensitivities of yet to be built
experiments. Neutrinos are the unique probe of physics not
accessible by accelerators like the Large Hadron Collider, and
therefore improving our knowledge about neutrinos is highly
complementary to traditional collider physics.
Minic has been concentrating his effort on understanding how the quarks and gluons (particles in the upper half of the chart) interact with each other to form baryons, mesons, and glueballs. Baryons are a class of particles that comprise the proton and the neutron which are the basic building blocks of atomic nuclei. Understanding how they are formed from quarks will be a major breakthrough in our understanding of what we are made of.
Mizutani has been interested in the interactions among mesons and baryons, i.e. bound states of two and three quarks, respectively, at relatively low energies. For the time being, he is particularly interested in the properties of mesons which contain at least one charm "c" quark put in a dense and/or hot matter formed in collisions between two large nuclei like gold or lead at extremely high energies. Such an environment is expected to have taken place at a very early stage of the universe, or after massive stars have ended their lives to become extremely compact and dense objects. The main theoretical tool employed in his approach is the use of symmetries to constrain the effective hadronic interactions: the symmetry among the very light (u, d, s) quarks is called chiral symmetry, and that among the heavy (c and b) quarks is called heavy quark symmetry.
Sharpe has been interested in understanding what quarks, gluons, and the other particles in the chart above are made of. Together with Minic, he works on various problems in string theory, one current attempt is to reconcile particle physics and general relativity. String theory says that each of the particles in the chart above can be understood as a vibration of a one-dimensional object, known as a string. Furthermore, many developments in string theory have had spinoffs which gave more direct insight into particle physics, for example the understanding of strong coupling physics in certain ("supersymmetric") models of quarks and gluons. Although string theory is not directly testable experimentally, there are many indirect tests that can be performed via, for example, the mathematical predictions of string theory, and so he is also interested in mathematical aspects of the subject.
Takeuchi has been interested in figuring out what can be inferred about new physics (particles and interactions that are yet to be discovered) from precision measurements of how the Z and W interact with the quarks and leptons. Most recently, he has been looking at how one flavor of neutrino changes into another (neutrino oscillations) in the presence of matter, and studying what an experimental measurement of the process can potentially tell us about the unknown.
|
