Engineering topics
Jenkins, D.
Publications and source records attributed to Jenkins, D..
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.
Data analysis techniques, differential cross sections, and spin density matrix elements for the reaction γp → Φp
High-statistics measurements of differential cross sections and spin density matrix elements for the reaction γ p → Φp have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.97 to 2.84 GeV, with an extensive coverage in the Φ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the Φ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- (Φ → K⁺K⁻) and neutral- (Φ → K 0 S K 0 L ) $K\bar{K}$ decay modes of the Φ. Further, for the charged mode, we differentiate between the cases where the final K⁻ track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed Φ mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide √s bins for the charged- and the neutral-mode, respectively. Possible effects from K⁺Λ* channels with p$K\bar{K}$ final-states are discussed. These present results constitute the most precise and extensive Φ photoproduction measurements to date and in conjunction with the ω photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.
Well Developed Deformation in Si 42
For this research, excited states in 38,40,42 Si nuclei have been studied via in-beam γ-ray spectroscopy with multinucleon removal reactions. Intense radioactive beams of 40 S and 44 S provided at the new facility of the RIKEN Radioactive Isotope Beam Factory enabled γ-γ coincidence measurements. A prominent γ line observed with an energy of 742(8) keV in 42 Si confirms the 2 + state reported in an earlier study. Among the γ lines observed in coincidence with the 2 + → 0 + transition, the most probable candidate for the transition from the yrast 4 + state was identified, leading to a 4 1 + energy of 2173(14) keV. The energy ratio of 2.93(5) between the 2 1 + and 4 1 + states indicates well-developed deformation in 42 Si at N = 28 and Z = 1 . Also for 38,40 Si energy ratios with values of 2.09(5) and 2.56(5) were obtained. Finally, together with the ratio for 42 Si, the results show a rapid deformation development of Si isotopes from N = 24 to N = 28.
Comparison of forward and backward p p pair knockout in 3 He ( e , e ' p p ) n
Measuring nucleon-nucleon Short Range Correlations (SRC) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wavefunction, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the 3 He(e,e'pp)n reaction, looking at events with high momentum protons (p p > 0.35 GeV/c) and a low momentum neutron (p n < 0.2 GeV/c). We examined two angular configurations: either both protons emitted forward or one proton emitted forward and one backward (with respect to the momentum transfer, → q). Thus, the measured relative momentum distribution of the events with one forward and one backward proton was much closer to the calculated initial-state pp relative momentum distribution, indicating that this is the preferred configuration for measuring SRC.
Codeless GPS Applications to Multi-Path: CGAMP
Cordless Global Positioning System (GPS) Applications to Multi-Path (CGAMP) is meeting the challenge of exploiting the L-band signals from the Global Positioning System (GPS) satellites for the measurement of the impulse response of radio transmission channels over space-Earth paths. This approach was originally suggested by E. K. Smith and has been pursued by J. Lemmon, without an affordable implementation being identifiable. In addition to the high cost of a suitable P code correlating GPS receiver, there is also the major impediment of the often announced Department of Defense policy of selective availability/anti-spoof (SA/AS) that clouds reliable access to the wideband (20 MHz) P channel of the GPS signals without cryptographic access. A technique proposed by MacDoran utilizes codeless methods for exploiting the P channel signals implemented by the use of a pair of antennas and cross correlation signal detection.
Tissue enzyme studies in Macaca nemestrina monkeys.
Total enzyme activities in fresh tissue specimens from major organs of Macaca nemestrina were analyzed for lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and aldolase. The concentration of these enzymes varied among the different tissue with skeletal muscle, heart, and brain having the highest activities. LDH isozymes determinations for the various tissues were also made. The spectrum of LDH isozyme distribution appears to be quite specific and characteristic for at least some of the tissues analyzed.
Status report on the biosatellite
NASA biological science experimental program for Gemini