Electromagnetic Form Factors of the Nucleon and Compton Scattering

We review the experimental and theoretical status of elastic electron scattering and elastic low-energy photon scattering (with both real and virtual photons) from the nucleon. As a consequence of new experimental facilities and new theoretical insights, these subjects are advancing with unprecedented precision. These reactions provide many important insights into the spatial distributions and correlations of quarks in the nucleon.Comment: 47 pages, 18 figures, includes corrections and updates to published manuscrip

Nuclear Charge Density Distributions from Elastic Electron Scattering Data

The model independent procedure of extracting charge density distributions from elastic electron scattering data is investigated. The charge density distributions are expanded on an orthonormal basis and the parameters of the expansions are fixed by the comparison with the experimental data. Two bases with different analytical properties (Fourier-Bessel and Hermite) are used. This allows us to disentangle the uncertainties coming from the choice of the expansion basis from those intrinsic to the extraction procedure. We design a set of tests to select the number of the expansion coefficients adequate for a proper description of the data. The procedure is applied to elastic data measured on $^{12}$C, $^{40}$Ca and $^{208}$Pb nuclei.Comment: 17 pages, 11 figures available on request to [email protected], to be published in Nucl.Phy

Revitalization and Initial Testing of a Blowdown Supersonic Wind Tunnel

The Supersonic tunnel located in Patterson Labs at Mississippi State University has been thoroughly documented for future reference purposes. Data acquisition, physical components, shutdown devices, a control program, and the hydraulic system are all discussed in detail. Analysis is performed showing that the flow within the Mach 2 nozzle only reaches Mach 1.8 for a portion of the flow, but that this portion of the flow is relatively stable for a wide range of settling chamber pressures. It is concluded that the tunnel with the nozzle blocks used functions correctly

Revitalization and Initial Testing of a Blowdown Supersonic Wind Tunnel

The Supersonic tunnel located in Patterson Labs at Mississippi State University has been thoroughly documented for future reference purposes. Data acquisition, physical components, shutdown devices, a control program, and the hydraulic system are all discussed in detail. Analysis is performed showing that the flow within the Mach 2 nozzle only reaches Mach 1.8 for a portion of the flow, but that this portion of the flow is relatively stable for a wide range of settling chamber pressures. It is concluded that the tunnel with the nozzle blocks used functions correctly

Driving alkali Rydberg transitions with a phase-modulated optical lattice

We develop and demonstrate a spectroscopic method for Rydberg-Rydberg transitions using a phase-controlled and -modulated, standing-wave laser field focused on a cloud of cold $^{85}$Rb Rydberg atoms. The method is based on the ponderomotive (${\bf{A}}^2$) interaction of the Rydberg electron, which has less-restrictive selection rules than electric-dipole couplings, allowing us to probe both $nS_{1/2}\rightarrow nP_{1/2}$ and $nS_{1/2}\rightarrow (n+1)S_{1/2}$ transitions in first-order. Without any need to increase laser power, third and fourth-order sub-harmonic drives are employed to access Rydberg transitions in the 40 to 70 GHz frequency range using widely-available optical phase modulators in the Ku-band (12 to 18 GHz). Measurements agree well with simulations based on the model we develop. The spectra have prominent Doppler-free, Fourier-limited components. The method paves the way for optical Doppler-free high-precision spectroscopy of Rydberg-Rydberg transitions and for spatially-selective qubit manipulation with $\mu$m-scale resolution in Rydberg-based simulators and quantum computers

Measurement of the Proton's Neutral Weak Magnetic Form Factor

We report the first measurement of the parity-violating asymmetry in elastic electron scattering from the proton. The asymmetry depends on the neutral weak magnetic form factor of the proton which contains new information on the contribution of strange quark-antiquark pairs to the magnetic moment of the proton. We obtain the value $G_M^Z= 0.34 \pm 0.09 \pm 0.04 \pm 0.05$ n.m. at $Q^2=0.1$ (GeV/c)${}^2$.Comment: 4 pages TEX, text available at http://www.krl.caltech.edu/preprints/OAP.htm

Preliminary evidence of dual-marked lymphocytes in thoracic duct lymph fluid

Thoracic duct lymphocytes from patients receiving thoracic duct drainage as a pretransplant therapy were examined for cell surface markers. Patients followed over the drainage time period showed a variable but decreasing percentage of E-rosette-positive cells in the lymph fluid. A substantial percentage of these E-rosette-positive cells also had C3 receptors on their cell surface. Reactions of the whole lymphocytes with a heteroantisera to human B-lymphocyte antigens reflected the increasing proportion of B cells in the sample, but also indicated that a fraction of the T cells have Ia-like antigens on their surface. Some cells may have all 3 surface marker characteristics. Significance of these cells with respect to graft survival is discussed

Rydberg-EIT of 85^{85}Rb vapor in a cell with Ne buffer gas

We investigate Rydberg electromagnetically induced transparency (EIT) of $^{85}$Rb atomic vapor in a glass cell that contains a 5-Torr neon buffer gas. At low probe power, EIT lines exhibit a positive frequency shift of about 70~MHz and a broadening of about 120~MHz, with minimal dependence on the principal quantum number of the Rydberg states. The EIT line shift arises from s-wave scattering between the Rydberg electron and the Ne atoms, which induces a positive shift near 190~MHz, and from the polarization of the Ne atoms within the Rydberg atom, which adds a negative shift near -120~MHz. The line broadening is largely due to the Ne polarization. Our experimental results are in good qualitative agreement with our theoretical model, in which the shift is linear in buffer-gas density. Our results suggest that Rydberg-EIT can serve as a direct spectroscopic probe for buffer-gas density at low pressure, and that it is suitable for non-invasive measurement of electric fields in low-pressure noble-gas discharge plasmas and in dusty plasmas

Inclusion of virtual nuclear excitations in the formulation of the (e,e'N)

A wave-function framework for the theory of the (e,e'N) reaction is presented in order to justify the use of coupled channel equations in the usual Feynman matrix element. The overall wave function containing the electron and nucleon coordinates is expanded in a basis set of eigenstates of the nuclear Hamiltonian, which contain both bound states as well as continuum states.. The latter have an ingoing nucleon with a variable momentum Q incident on the daughter nucleus as a target, with as many outgoing channels as desirable. The Dirac Eqs. for the electron part of the wave function acquire inhomogeneous terms, and require the use of distorted electron Green's functions for their solutions. The condition that the asymptotic wave function contain only the appropriate momentum Q_k for the outgoing nucleon, which corresponds to the electron momentum k through energy conservation, is achieved through the use of the steepest descent saddle point method, commonly used in three-body calculations.Comment: 30 page