Experimental High Energy Physics

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Professors R.A. Briere, A. Engler - emeritus, T.A. Ferguson, M. Paulini, J.S. Russ, and H. Vogel

Particle physics has made great strides in recent decades, culminating in the creation and detailed testing of the Standard Model of particles and interactions. But our work is far from complete. Two general areas of great current interest are precision measurements and searches for new phenomena.

Each of the Carnegie Mellon experimental groups addresses both areas in their research portfolio. Quantities which can be cleanly interpreted are useful to over-constrain the Standard Model and perhaps expose its limitations. These include the search for B_s mixing and the measurement of CP violation in mixing (CDF) and studies of semileptonic B and D meson decays (CLEO). In some cases, interpretations are aided by lattice QCD calculations; checks on the reliability of such calculations are forthcoming (CLEO-c). New phenomena include those predicted in the standard model but not yet seen, such as the Higgs Boson (CDF, CMS) and glueballs (CLEO). In addition, searches for physics beyond our current model such as supersymmetric partners of known particles (CDF, CMS) will continue to be very active. There is also a good synergy with our theory group at CMU, which has worked in the areas of quark mixing phenomenology, heavy quark physics, lattice QCD, and new phenomena.

One experimental group, consisting of Professors Briere, Ferguson and Vogel is active on the CLEO experiment which operates at the Cornell Electron Storage Ring (CESR). CESR is a 10 GeV electron-positron accelerator which is a major center for studying B mesons and their associated Upsilon resonances. The CLEO experiment has been in existence for over 20 years, though the detector and accelerator have undergone many upgrades during that time. The CLEO collaboration has acquired a huge data set during its previous years of running, and has just installed a powerful new detector to continue doing important heavy-quark physics. The range of physics topics that can be explored with the CLEO experiment is very large. Future running on the Psi (charm quark) resonances planned for the CLEO-c era will further increase this range. The CMU group is responsible for dE/dx calibration and is currently pursuing analyses involving B mesons, D mesons, and the Upsilon resonances.

For the longer range future, the group is also involved with the Compact Muon Solenoid (CMS) detector for the Large Hadron Collider (LHC). The LHC is a proton-proton colliding beam accelerator to be built at CERN, with a center-of-mass energy of 14 TeV. When the LHC is finished in 2006, it will be the highest energy accelerator in the world. We are currently constructing state-of-the-art electronics for the endcap muon system of the CMS detector. This is a crucial part of the experiment and consists of about 150,000 channels of electronics.

Professors Russ and Paulini study particle physics at the world's highest available energies. Their group is working with the Collider Detector at Fermilab (CDF) which is operating at the Tevatron Collider. Among other significant measurements, the Fermilab experiments CDF and D0 made the first observation of the long-sought top quark in 1995. After a five year upgrade of the CDF detector and improving the Tevatron accelerator, the CDF collaboration has started in March 2001 for a 5-year data taking period to collect a greatly-expanded data set. There is a high expectation that these data might contain the first definite evidence for the existence of the Higgs boson, one of the foundation particles of the Standard Model of high energy interactions. The CMU group on CDF is interested in heavy flavor physics, in particular in the physics of B hadrons. The group plans to make some unique measurements of b-quark decays that will challenge our understanding of the process of CP violation in the weak interaction. Their group is also involved in the CDF hadron calorimeter project and responsible for the overall coordination of the CDF detector simulation. They are also members of the CDF upgrade proposal to prepare the silicon detector for high-luminosity operation in 2004.

A major modification of the CDF detector is also on the horizon. After a few years of operation, improved accelerator performance will result in so much beam to the experiment that the detectors will have to be improved. The CMU group is now involved in early planning for how to handle the higher rates with improved tracking and triggering performance. This involves electronic design, computational simulation, and new data analysis methods to extend the physics capabilities of CDF.

Recent Ph.D.s and Post-Graduation Positions
Alexander Kushnirenko (2000) “Precision Measurements of the and Lifetimes.” (Advisor: Russ); Postdoctoral scientist, Fermilab

HyangKyu Park (1998) “Measurement of the Rate of Charm Quark Pairs Produced by Radiated Gluons in Hadronic Z Decay.” (Advisors: Kraemer, Vogel); Research Associate, Univ. of Michigan

Prakash Mathew (1997) “Construction and Evaluation of a High Resolution Silicon Microstrip Tracking Detector and Utilization to Determine Interaction Vertices.” (Advisor: Russ); General Electric Medical Systems, Staff Engineer

Juan Carlos Pinto (1997) "Measurement of the B0-B0 bar Oscillation Frequency"; (Advisor: Engler);Research Scientist, KLA Tencor,

Jianming You (1996) "Measurement of the Hadronic Cross Section at the Z Resonance and Determination of Electroweak Parameters"; (Advisor: Ferguson);Staff Scientist, Beams Division, Fermilab

Jayant Shukla (1994) "Measurement of the Polarization of Tau Leptons from Z0 Decays"; (Advisor: Vogel); Research Associate, CERN

Stephen C. Timm (1994) "Production Polarization of the Sigma-minus and Xi-minus Baryons and the Radiative Decay of the Sigma-plus Baryon;" (Advisor: Russ); Staff Scientist, Computing Division, Fermilab

Guohua Wang (1993) "Measurement of the B-B-bar Forward-Backward Asymmetry and B0-B0-bar Mixing"; (Advisor: Ferguson); City Bank, NY

Song Yang (1993) "Charmed Baryon Lambda-c-+ Decays with a S+ in the Final State and Decay Asymmetry Parameters"; (Advisor: Procario); Wall Street

Chong Zhang (1993) "Measurement of the Branching Ratio for D ->K-(892)0-mu-neutrino and Search for Coherent Charm Production in 800 GeV/c Proton-Silicon Interactions"; (Advisor: Edelstein); Staff Scientist, Motorola

William Nichols (1991) "Charm Production in 800 GeV/c Proton-Emulsion Interactions"; (Advisor: Edelstein); Research Staff, Bettis Atomic Power Laboratory

Xiarong Shi (1991) "Determination of the Number of Neutrino Generations"; (Advisor: Vogel); Research Staff, Livermore Labs

Arne Freyberger (1990) "Production Correlations of Hadronically Produced Charmed Particles"; (Advisor: Lipton); Research Staff, Jefferson National Accelerator Facility

Yang-Ling Zhang (1989) "Hadronic Production of D* Mesons"; (Advisor: Russ); Staff Scientist, Lucent