Gregg Franklin

Professor and Department Head, Physics

Education

Research

Research in medium energy physics explores the boundary between nuclear and particle physics. As part of the Carnegie Mellon University Medium Energy Group, Prof. Franklin is involved in an experimental program exploring the constituents of neutrons and protons using high-precision electron scattering at the Thomas Jefferson National Accelerator Laboratory (JLab). In some of the experiments, a high-energy beam of polarized electrons is used in measurements that achieve accuracies of one part in a million. These experiments determine the strength of the parity-violating weak interaction and this information is used to separate out the contributions of up-, down-, and strange-quarks (and their anti-particle partners) to the properties of the proton and neutron. Other experiments use polarized targets to provide additional links between the electromagnetic properties of nucleons and their constituents.

The Medium Energy Group is known for its work in detector development. Prof. Franklin is currently overseeing the design and construction of a new hadron calorimeter that will be used in a suite of experiments as part of JLab's SuperBigbite spectrometer program. This program will take advantage of JLab's energy-upgrade, a new large-acceptance spectrometer, and new detector packages to lend insight into the quark-structure of nucleons. The Medium Energy Group is also contributing to the upgrade of JLab Hall A's Compton Polarimeter. This device is designed to use the known spin-dependence of electron-photon scattering to determine the spin-polarization of the JLab electron beam to an accuracy of better than 1%.

Selected Publications

• S. Abrahamyan et al., New Measurements of the Transverse Beam Asymmetry for Elastic Electron Scattering from Selected Nuclei, Physical Review Letters 109, 192501 (2012)
• C.J. Horowitz  et al., Weak charge form factor and radius of ²⁰⁸Pb through parity violation in electron scattering, Physical Review C 85, 032501 (2012)
• S. Abrahamyan  et al., Measurement of the Neutron Radius of ²⁰⁸Pb through Parity Violation in Electron Scattering, Physical Review Letters 108, 112502 (2012)
• Z. Ahmed et al., New Precision Limit on the Strange Vector Form Factors of the Proton, Physical Review Letters 108, 102001 (2012)
• M. Friend et al., Upgraded photon calorimeter with integrating readout for the Hall A Compton polarimeter at Jefferson Lab, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 676, 96-105 (2012)
• M. Friend,  G.B. Franklin, B. Quinn, An LED pulser for measuring photomultiplier linearity, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 676, 66-69 (2012)
• D. Androić et al., Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasielastic Electron-Deuteron Scattering, Physical Review Letters 107, 022501 (2011)
• D. Androić et al., The G0 experiment: Apparatus for parity-violating electron scattering measurements at forward and backward angles, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 646, 59-86 (2011)
• S. Riordan et al., Measurements of the Electric Form Factor of the Neutron up to Q²=3.4  GeV² Using the Reaction ³He(ee^′n)pp, Physical Review Letters 105, 262302 (2010)
• D. Androić et al., Strange Quark Contributions to Parity-Violating Asymmetries in the Backward Angle G0 Electron Scattering Experiment, Physical Review Letters 104, 012001 (2010)
• M. Ukai et al., γ-ray spectroscopy of _Λ¹⁶O and _Λ¹⁵N hypernuclei via the O¹⁶(K^-,π^-γ) reaction, Physical Review C 77, 054315 (2008)
• J. Parker et al., Weak decays of _Λ⁴He, Physical Review C 76, 035501 (2007)
• K. Paschke et al., Experimental determination of the complete spin structure for p̅p→Λ̅Λ at p_p̅ = 1.637 GeV/c, Physical Review C 74, 015206 (2006)
• R. Stotzer et al., Search for the H-Dibaryon in ³He(K^-,K⁺)Hn, Physical Review Letters 78, 3646-3649 (1997)
• J. Szymanski et al., Nonleptonic weak decay of He_Λ⁵ and C_Λ¹², Physical Review C 43, 849-862 (1991)