Rutgers University Department of Physics and Astronomy

2000-01 Handbook for Physics and Astronomy Graduate Students

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Research Programs

Experimental Elementary Particle Physics

A lively area of experimental work in the department is High Energy Physics. Eight faculty members supervise efforts involving roughly forty people (physicists, technical and clerical staff, graduate and undergraduate students) in a wide spectrum of elementary particle investigations. These efforts are well supported by the National Science Foundation, the Department of Energy and the University, and they have had considerable success in obtaining precious beam time at large accelerator facilities. At Rutgers, there are extensive resources for the construction and testing of detectors and electronics used in experiments, and dedicated computers for the analysis of the resulting data. Grants in this area provide financial support for advanced graduate students to spend full time on research, and they do not have to teach to earn an income.

Professors John Conway, Thomas Devlin, Amit Lath, Sunil Somalwar and Terence Watts

Rutgers is a collaborator in the construction and operation of CDF (Collider Detector at Fermilab), a $100-million-plus facility which detects the particles resulting from 2-TeV proton-antiproton collisions. This facility is, and for much of the coming decade will remain, the premier facility on the planet for studying fundamental interactions at highest possible energy. The data already gathered from this facility over the past decade has yielded the discovery of the very massive top quark, the first evidence for violation of CP symmetry in the decay of B-mesons, very precise measurements of the mass of the W vector boson, the discovery of the B_c which is the last meson in the standard model, and many other results at the energy frontier of physics. These studies use CDF's excellent detection efficiency for jets, photons, leptons, and missing neutral particles.

We have been analyzing data from earlier runs and working to upgrade the CDF detector. We start a new phase of data collection with a greatly improved accelerator and detector early in 2001. We will search for new W and Z bosons, evidence of compositeness in quarks, gluons, and other new phenomena available in this new collision energy range. Very high priority will go to searching for new phenomena such as the Higgs boson and super-symmetric particles. We expect greatly improved precision in measurements of CP violation in B-mesons.

In past runs of CDF, Rutgers created and developed the Level 3 trigger which analyzed and selected the few rare and interesting events from up to a million interactions per second. In preparation for future runs, we have turned our attention to two key areas: the development of silicon microstrip detectors which are the key detector element in identifying very short-lived tracks, and the infrastructure for offline data processing to make the complex data sets readily available for physics analysis.

Students, both undergraduate and graduate, have always been a key part of the high energy physics effort at Rutgers. The data coming from the CDF facility offer an extraordinarily wide range of choices for learning experimental and analytical techniques and for thesis topics at the frontier of physics.

Professors Richard Plano and Mohan Kalelkar

We are working on the analysis of data from an experiment called SLD at the Stanford Linear Collider, studying electron-positron interactions at 91 GeV, the mass of the neutral weak boson Z. A unique feature is high polarization of the electrons. One of our primary goals is to test the Standard Model by making precision measurements of certain polarization-sensitive asymmetries. SLD has already provided the single most sensitive measurement of the weak mixing angle, a crucial parameter in the Standard Model. The narrow beams at the Linear Collider also allow precise studies of the bottom quark (B mesons), which, along with the top quark, belong to the least well understood sector of the Standard Model. SLD will measure B lifetimes as well as the intriguing phenomenon of B/Anti-B "mixing". A wealth of other physics topics will be addressed, such as measuring the lifetime and other properties of the tau lepton. Heavy quark physics will be studied by measuring bottom and charm partial widths of the Z boson. QCD, the gauge theory of the strong force, will be tested using measurements of the color charges of quarks and gluons, polarization of leading baryons, jet handedness, and flavor tests. For more information, see SLD at Rutgers.

Professors Stephen Schnetzer, Sunil Somalwar, and Gordon Thomson

We are concluding our participation in the KTeV experiment at Fermilab. This experiment involves research on the source of the violation of Charge-Parity (CP) symmetry using a beam of neutral K mesons. CP violation is one of the least understood aspects of the current Standard Model of particle physics. It is believed to be related to the matter-antimatter asymmetry that became manifested in the early universe. Determining whether the magnitude of CP violating amplitudes are consistent with the Standard Model is currently one of the most important issues confronting particle physics. Since the KTeV experiment is a relatively small High Energy Physics experiment, our students had the opportunity to master all aspects of research, such as hardware, software, and particle physics which is the driving force behind the experiment.

For the past ten years Professors Schnetzer, Conway, Plano, Somalwar, and Thomson have been developing diamond based detectors. This is an exciting program that was pioneered by our group at Rutgers and which is now attracting keen world-wide interest. Diamond detectors have many advantages over detectors based on more conventional technology. Most importantly, they are several hundred times more resistant to damage from ionizing radiation than detectors based on silicon. Diamond's radiation hardness will make possible many important physics studies at future high intensity facilities. Large area diamond detectors are made possible through the growth of diamond films by chemical vapor deposition (CVD). Through our efforts, the size of signals from CVD diamond has increased by a factor of 1000 over the past 10 years. Over the past several years we have been testing diamond detectors constructed as microstrip tracking devices. The real challenge, however, is to assemble and test diamond pixel detectors. Pixel detectors located very close to the interaction region are the likely first real application of diamond detectors. The Rutgers CDF group is currently developing a proposal to implement a diamond pixel detector for the 2005 CDF collider run. In the longer range, we are collaborating with several European and American institutions on developing diamond pixel detectors for the CMS experiment at the Large Hadron Collider at CERN

Professor Gordon Thomson

I am working on the High Resolution Fly's Eye Experiment (HiRes),which has the aim of studying the highest energy cosmic rays. Interactions between cosmic ray particles and photons of the cosmic microwave background radiation form an energy-loss mechanism for the cosmic rays, and limit protons which have traveled more than 50 Megaparsecs across intergalactic space to an energy lower than about 6*10**19 electron Volts. Since there are no known sources of such high energy particles within this distance we should see no cosmic rays above this energy. But our experiment (as well as three other experiments) has observed events above this cutoff. The experiment is located atop two desert mountains in west central Utah and consists of large mirrors which collect light from cosmic ray showers and focus it onto an array of photomultiplier tubes. As the shower propagates down through the atmosphere its image moves across the photomultiplier tubes and by recording the time the tubes fire and their pulse heights we can completely reconstruct the characteristics of the cosmic ray that initiated the shower. My group consists of a postdoctoral research fellow, graduate students and undergraduates, and we are collaborating with several other universities in the U.S. and Australia. We travel to Utah to work on the experiment and collect data, then analyze it using the excellent computer system we have here at Rutgers. I think of our experiment as one where high energy physics techniques are being employed to solve a problem in astrophysics.

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Revised November, 2000