Young-Kee Kim in the Library for Symmetry

Young-Kee Kim: Research

As an experimental scientist, I am working on particle physics whose goal is to understand how the universe works at the most fundamental level by discovering and understanding the fundamental constituents (called elementary particles) and the forces acting among them.

My main physics interest is understanding the orgin of mass for elementary particles (studies of the Higgs boson), and searching for dark matter and other new physics using the Higgs boson.

ATLAS at the LHC (2010 - ): A new particle, which behaves like the predicted Higgs, was discovered at mass of 125 GeV by the ATLAS and CMS experiments at the LHC at CERN in 2012 via processes in which this particle decayed into a pair of photos, Z bosons and W bosons (H → γγ, ZZ, WW). Francois Englert and Peter Higgs received the Nobel prize in 2013 for their theoretical discovery of the Higgs mechanism.

The most critical goal at the LHC over the coming years is to develop a deeper understanding of the nature of the Higgs particle. One key process yet to be observed is where the Higgs decays into a pair of bottom quarks (H → bb), the most frequent decay mode for the 125 GeV Higgs. This mode allows to study the Higgs boson's coupling to fermions (such as electrons and quarks) and to probe directly the mechanism for fermion mass generation via the Higgs. Many well-motivated new physics models predict significant deviations to the H → bb Standard Model rate. Thus this decay channel will be a good tool to explore new physics models.

Observing and studying H → bb, and searching for dark matter particles in the H(→bb) + dark matter process are my main interests and current activities of my group. These tasks will require significant improvements of b-jet triggers using the new tracking trigger (FTK) combined with the LHC accelerator and detector upgrades. In the past few years, my research group (students and postdocs) has been heavily involved in the FTK (hardware and simulation) that has more capability and flexibility than the current trigger system. In addition, my group searches for a new vector boson that decays into top and bottom quarks.

CDF at the Tevatron (1990 - 2013): At CDF experiment, my group measured the masses of the W boson and the top quark very precisely (numerous measurements were made using different decade modes, different datasets and different analysis techniques). These measurements predicted the mass of the Higgs boson (the "core" of the very successful theory of particle physics, the Standard Model, and thought to be key to understanding why elementary particles have mass) to be less than 145 GeV.

My group has also involved other topics measuring the diboson production process whose final states are similar to those of the Higgs boson process (this is an important step for designing Higgs searches), the Bs oscillation, the lifetime of the top quark (by measuring its width), the mass difference between the top and anti-top quarks, properties of the Z and W boson (their production cross section and forward-backward asymmetry), and decay rates of bottom and charm mesons.

Accelerator Physics (2009 - ): Although accelerator physics is an active research field, and accelerators are critical for particle physics research and other research areas in science, the U.S. has not been educating and training enough accelerator students. Thus, I have been giving some of my time to educating and training students in accelerator physics. The following is the list of topics and Ph.D. students:

  • Satomi Shiraishi: "Laser driven wakefield accelerator - Staging experiment"
  • Tim Zolkin: "Studies of beam dynamics at Fermilab Booster accelerator" and "Studies of non-linear lattice"
  • Alexander Vostrikov: "Achieving ultra high Q in superconducting niobium cavities"
  • Sergey Antipov: "Demonstration of beam properties requred for Project X superconducting RF linac"
  • Alexey Kochemirovsky: "Design and simulation of the vacuum muon cooling channel and experimental studies"
Physics 335 Projects for any 1st year grad. students - see here

Happy to have more graduate and undergraduate students for any of these subjects. Go to Young-Kee Kim's Homepage for contact information.