High Energy Physics

The goal of particle physics is to understand what are the most fundamental constituents of matter and how these elementary particles interact. The next few years hold great promise for answering fundamental questions such as

  • What is the origin of electroweak symmetry breaking and mass (the Higgs sector)?
  • Are there additional fundamental particles (e.g. supersymmetric partners of the known particles)?
  • What is the origin of the matter anti-matter asymmetry in the Universe?
  • What is dark matter?
  • What is dark energy?

Penn has a very active and strong elementary particle physics theory group . The central thread is the unification of all interactions. This includes theoretical efforts in string and brane theory, phenomenological studies of the electroweak interaction, and attempts to connect the fundamental theory with experiment. The puzzles of dark matter, dark energy and the nature of the early universe demand a joint venture between cosmology and particle physics. Penn has a new Center for Particle Cosmology that provides an incubator for such research, fostering the development of new theoretical approaches, grounded in the current epoch of remarkable experimental progress.


Experimentalists in the Penn faculty are working on the following projects:

  • The ATLAS experiment at the Large Hadron Collider (LHC) at CERN on the French-Swiss border. The goal of ATLAS is to discover new elementary particles. With data, there are lots of interesting topics for graduate students to work on, please join us! The detector started taking data in 2009 at a center-of-mass energy of 7 TeV, and has rapidly accumulated a large amount of data, with over 5 fb-1 collected by the end of the 2011 run. We have four faculty on ATLAS, working on the search for the origin of electroweak symmetry breaking in terms of the Higgs boson in the standard model, and on several searches for physics beyond the standard model. We are already involved in research and development for several upgrades to ATLAS, which will provide some very interesting hardware projects in the next years. It is expected that ATLAS will continue to take data in 2012, then shutdown for 2013-14 while LHC repairs take place to reach the design energy of 14 TeV, followed by data-taking for several years at 14 TeV. 
  • The Sudbury Neutrino Observatory in Ontario.  The results from this facility have provided revolutionary insight into the properties of neutrinos and the core of the sun.  The solar neutrinos produced by fusion interactions in the core of the sun are electron neutrinos.  En route from the sun to the earth, these electron neutrinos change into other types of neutrinos. The direct evidence for solar neutrino transformation also indicates that neutrinos have mass. The facilty commenced in 1999 and data taking was completed in 2006. A new experiment called SNO+ will reuse the detector to search for neutrinoless double beta decay as well as measuring the low-energy neutrino flux from the sun. We are involved in commissioning electronic upgrades, with first solar neutrino data expected in the next two years.
  • The Long Baseline Neutrino Experiment (LBNE) is focused on the areas of neutrino mixing that are least known. The primary physics is aimed at electron neutrino appearance measurements, with the highest priority being a search for a Standard Model-like CP-violating asymmetry in the oscillation of a muon neutrino into an electron neutrino with a beam originating at Fermi National Accelerator Laboratory. Penn has been involved in the physics and design for over a decade. The focus of our effort is the development of a 200 kt Cherenkov far detector. We have three primary efforts: photomultiplier characterization, simulation and reconstruction development, and front-end electronics design. This project is in a research and development phase for the next few years. 
  • The Penn instrumentation group provides an invaluable resource to the field of experimental particle physics, with expertise in detector design and electronics. We are involved in several research and development projects to upgrade the ATLAS detector and to develop the water Cherenkov detector for LBNE, and design and development of the camera for the Large Synoptic Space Telescope.

We have active seminar programs in Experimental Particle Physics and Theoretical Particle Physics at Penn.