P&A Brochure - High Energy

Elementary particle physics deals with the study of the ultimate constituents of matter and the nature of the interactions between them. Physicists from Johns Hopkins have a long history of contributions to the current understanding of the subatomic world known as the Standard Model.

The activities of the Experimental High Energy Physics group have included the investigation of electron-positron collisions at the Stanford Linear Accelerator Center (SLAC) and at the European Center for Particle Research (CERN), as well as the search for neutrino oscillations at Brookhaven National Laboratory (BNL) and at CERN. The current centerpiece of the experimental program is the Collider Detector at Fermilab (CDF). The faculty members now involved in these experiments are Professors Barnett, Blumenfeld, C.Y. Chien, Maksimovic, and Swartz.

CDF

At the Fermilab accelerator, protons are brought into collision with antiprotons at the highest energies currently available at any laboratory. The products of these collisions are observed with CDF and analyzed to search for new phenomena. In the last few years the Johns Hopkins group played a central role in the discovery of the top quark. The top was one of the last missing pieces of the Standard Model, and its detection was the most important result in particle physics in the last 10 years. The Hopkins group helped to build a crucial piece of the hardware, the Silicon Vertex Detector, which was used to identify bottom quarks coming from the top quark decay. The group also had a leading role in the data analysis.
Over the past seven years, the CDF experiment has undergone an extensive upgrade that will be matched by an order of magnitude increase in the proton-antiproton collision rate. This will make it possible to study further the top quark, to look for CP violation in reactions involving bottom quarks and to search for new phenomena beyond the Standard Model, such as supersymmetry, technicolor and the compositeness of quarks. The Johns Hopkins group is involved in commissioning the new Silicon Vertex Detector and in developing track reconstruction software and data analysis techniques. We are also involved in designs for another upgrade of the CDF detector to take place in 2005.

Former postdoc John Skarha working at Fermilab on the CDF Silicon Vertex Detector, which Hopkins physicists helped to construct.

    To continue the search for new phenomena at the highest possible collision energies, the Johns Hopkins group has joined the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider under construction at CERN in Geneva, Switzerland. This new facility, which is expected to be ready in 2007, is similar in concept to the Fermilab collider, but the collisions will have seven times the energy and 100 times the collision rate of the Fermilab machine. In order to exploit fully this challenging environment, the Hopkins group is developing pixel detectors, which are a technical extension of the silicon detectors of CDF that they work on now. The Hopkins group is working to develop a 16-million channel forward pixel system, which will be a key element of the central tracking system of the experiment. Work on design, development and tests is being carried out at Hopkins, until final construction begins in a few years.

    High energy experiments have five major phases: planning the overall experiment, with the associated development of detector prototypes, building the various elements of the detector, installing and debugging the full detector at the accelerator center, and taking the data and analyzing it. To gain experience in as many of these areas as possible, graduate students are encouraged to participate early in the research and development during their stay at Hopkins. There are opportunities for summer jobs and for first-year laboratory projects with members of the group. It is expected that graduate students will participate in most phases of an experiment and that they will play a major role in its running and analysis. Much of the planning of the experiment, development of prototypes and fabrication of the detectors is done on campus. However, students spend a significant period of time at the accelerator center for detector assembly and data taking. Data analysis may be done with the computers of the high energy group, or with the central computer facilities of the national or international laboratories. Particle physics graduate students gain a broad knowledge of fast electronics, detector techniques, accelerator theory and technology, data processing and computer techniques, and experience the excitement of confronting theoretical ideas at the forefront of the field with their experimental data.

    The particle theory group has been conducting research on a wide variety of topics, ranging from supersymmetry and supergravity to the properties of heavy quarks, neutrinos and cosmic rays. There is particular interest in understanding how new phenomena will be explored in the next generation of high energy physics experiments.

    Jonathan Bagger is continuing his study of supersymmetry and supergravity. In addition to his more formal work on the interconnections between string theory and field theory, he has been investigating the phenomenology of supersymmetry at high energy colliders.
    Gabor Domokos and Susan Kovesi-Domokos are working on the physics of the highest energy neutrinos, which are expected to be emitted from exotic astronomical objects, such as active galactic nuclei and gamma ray bursters. They have an ongoing collaboration with the experimental group from the universities of Athens and Florence, where researchers are building the NESTOR neutrino telescope. Its main purpose is to study the sky in "neutrino light."
    Adam Falk has been studying the production, decay and general behavior of bottom and charmed quarks. Systems containing these "heavy" quarks will be the focus of intense experimental attention over the next five years, as the B Factories at SLAC, KEK and Cornell come on line and start taking data. Interpreting the results of these experiments will require an understanding of the complicated dynamics that binds these quarks into observable hadrons. Falk's research has focused on unraveling these effects.
    Raman Sundrum focuses on theoretical mechanisms and observable implications of extra spacetime dimensions, supersymmetry, and strongly coupled dynamics.
    Chung W. Kim has been engaged in the theoretical investigation of neutrino oscillations, which continue to play a major role in the study of neutrino mass. He is also analyzing the effects of gravitation and finite temperature on neutrino oscillations. Practical applications to solar, atmospheric and supernova neutrinos are also being investigated.

    The interactions among students, faculty and postdoctoral fellows in high energy theoretical physics are frequent and informal. They meet at seminars and often encounter one another in the hall. Since their offices are located on the same floor, informal exchanges are simple. Students thus have easy access not only to their dissertation supervisors but to other faculty as well.

Faculty: Bagger, Barnett, Blumenfeld, C.Y. Chien, Domokos, Falk, Fulton (emeritus), Kim, Kovesi-Domokos, Maksimovic, Morava (Mathematics), Pevsner (emeritus), Sundrum, Swartz.