Physics Commons^™

Measurement Of The Spin Structure Function Gd1 Of The Deuteron And Its Moments At Low Q2, Krishna P. Adhikari

Physics Theses & Dissertations

Double polarization cross section differences (Δσ ||) for proton and deuteron targets have been measured in the EG4 experiment using the CLAS detector at Jefferson Lab. Longitudinally polarized electron beams at relatively low energies of 1.056, 1.337, 1.989, 2.256 and 3.0 GeV from the CEBAF accelerator were scattered off longitudinally polarized NH₃ and ND₃ targets. Scattered electrons were recorded at very low scattering angles (down to θ= 6°) with the help of a new dedicated Cherenkov counter and a special magnetic field setting of the CLAS detector in order to measure the cross section differences in the …

Characterization Of Microwave Discharge Plasmas For Surface Processing, Milka Nikolic

Physics Theses & Dissertations

We have developed several diagnostic techniques to characterize two types of microwave (MW) discharge plasmas: a supersonic flowing argon MW discharge maintained in a cylindrical quartz cavity at frequency ƒ = 2.45 GHz and a pulse repetitive MW discharge in air at ƒ = 9.5 GHz. Low temperature MW discharges have been proven to posses attractive properties for plasma cleaning and etching of niobium surfaces of superconductive radio frequency (SRF) cavities. Plasma based surface modification technologies offer a promising alternative for etching and cleaning of SRF cavities. These technologies are low cost, environmentally friendly and easily controllable, and present a …

Spin Dependence In Polarized Proton-Proton Elastic Scattering At Rhic, Donika Plyku

Physics Theses & Dissertations

The STAR (Solenoidal Tracker At RHIC - Relativistic Heavy Ion Collider) experiment is equipped with Roman Pots, insertion devices that allow detectors to be moved close to the beam for the measurement of high energy protons scattered at very small angles. This setup, together with the unique capability of RHIC to collide spin-polarized proton beams, allows STAR to study both the dynamics and the spin-dependence of the proton-proton ( pp) elastic scattering process. Silicon strip detectors, installed inside the Roman Pots, measure tracks of protons scattered diffractively at very small angles. In a dedicated run with special beam optics …

Three-Point Correlator And Pion Form Factor In Quantum Chromodynamics: Methods Of Calculation For Two-Loop Spectral Density, Islam Bedir

Physics Theses & Dissertations

The methods are developed of two-loop calculation of spectral density for the 3-point correlation function of an electromagnetic current and two axial currents which are the basis of the pion form factor analysis within the framework of QCD sum rules and local quark-hadron duality approach. The nature of various types of contributions is established which are related to particular regions of momentum integrations inside Feynman integrals. The trace factors accompanying all six two-loop diagrams are calculated and classified. To regularize particular loop integrals, the dimensional regularization technique has been used. The calculation involves such methods as infinite-momentum frame approach, alpha-representation …

Double Spin Asymmetry In D →(E→E'P)N, Michael Mayer

Physics Theses & Dissertations

Using the CLAS detector at Jefferson Lab, double spin asymmetries (A ∥) for quasi-elastic electron scattering off the deuteron have been measured at several beam energies. The data were collected during the EG1 experiment, which scattered longitudinally polarized electrons with energies from 1.6 to 5.8 GeV off a longitudinally polarized cryogenic ND₃ target. The double spin asymmetries were measured as a function of photon virtuality Q² (0.13-3.17 (GeV/c)2), missing momentum (0.0-0.5 GeV/c), and the angle between the (inferred) "spectator" neutron and the momentum transfer direction (θ_ng). The results from EG1b are compared with a recent model …

Measurement Of Polarized Proton-Proton Elastic Scattering At The Relativistic Heavy Ion Collider (Rhic), Ivan Koralt

Physics Theses & Dissertations

Elastic proton-proton (pp) scattering is one of the most fundamental processes in nature and yet, it is one of the most difficult to describe. There are two interactions involved in this process: electromagnetic (Coulomb) and hadronic (strong) interactions. Underlying exchange mechanisms of these two interactions are the virtual photon and the Pomeron exchange, respectively. The difficulty of elastic pp scattering arises from the fact that the nature of the Pomeron and its exchange are not well understood and need a theoretical approach, which is still under development.

At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab …

Visualizing And Understanding Tectonism And Volcanism On Earth And Other Terrestrial Bodies, Mladen M. Dordevic

Physics Theses & Dissertations

This dissertation presents new methods of visualizing, teaching, assessing, modeling, and understanding tectonics on Earth and other celestial bodies. Tectonics is the study of planetary lithospheres and includes impact, plate, plume, cryo- and gravitational mechanisms. This dissertation is concerned with plate tectonics and plate/mantle plume interactions. Plate tectonics describes the mainly horizontal motion of lithospheric plates over the asthenosphere. Lithosphere is created at ridges and consumed at subduction zones. In addition to the plate tectonic system, mantle plumes also contribute to mass motions in the subsurface Earth. Both plate tectonics and plume upwelling processes help shape the present form of …