Medium Energy Physics generally concentrates on the middle ground between conventional nuclear physics and high energy particle physics, although the boundaries are not sharply defined. We are generally interested in problems in which the quark structure of hadrons (strongly interacting particles) is relevant. The energy range of interest in Medium Energy Physics doesn't usually lend itself to the simplifications of a perturbative treatment of quantum-chromodynamics. Rather, it allows us to explore a wealth of important topics, such as the structure of the hadrons themselves, which are intrinsically non-perturbative. 

The Carnegie Mellon medium energy group has participated in a rich variety of experiments over the past few years, using anti-protons to study annihilation on protons with the resulting creation of strange (and anti-strange) quarks; kaons and pions to study the weak decay of hypernuclei and to search for un-discovered states such as the H-dibaryon; and photons and electrons to probe strangeness production and the structure of the neutron. We have contributed to many aspects of these experiments: detectors, data-acquisition hardware, on-line acquisition programs and analysis. Carnegie Mellon graduate students have taken a leading role in the analysis and interpretation of the data from many of these experiments. 

A high-current superconducting electron accelerator facility, Jefferson Laboratory (JLab), came into operation a few years ago in Virginia. This is now an important center of Medium Energy research, and the venue for most of our experiments. I have been leading our group's involvement in the G⁰ experiment which will use the JLab beam to study the weak form-factors of the proton and which may provide new information on the strangeness content of the nucleon. 

D. March and et al. (The G0 collaboration, Jefferson Lab, Newport News, VA), “G0 electronics and data acquisition (forward-angle measurements)”, accepted for publication in Nuclear Instruments and Methods.

R.K. Bradford et al. (the CLAS collaboration) “First measurement of beam-recoil observables Cx and Cz in hyperon photoproduction”, Phys. Rev. C 75 (2007) 35205.

K.D. Paschke, B. Quinn, et al. (The PS185 collaboration), “Experimental determination of the complete spin structure for antiproton + proton annihilation to  anti-Lambda + Lambda  at antiproton momentum = 1.637 GeV/c”,  Phys. Rev. C 74 015206 (2006).

D.S. Armstrong, et al.  (The G0 collaboration, Jefferson Lab, Newport News, VA)  “Strange-quark contributions to parity-violating asymmetries in the forward G0 electron-proton scattering experiment”, Phys. Rev. Lett. 95 (2005) 092001.

B. Bassalleck, et al. (The PS185 collaboration),  “Measurement of Spin-Transfer Observables in proton + anti-proton annihilation to Lambda + anti-Lambda at 1.637 GeV/c”,  Phys. Rev. Letters 89 (2002) 212302.