The Q-weak experiment at Thomas Jefferson National Accelerator Facility (USA) will make a precision determination of the proton weak charge with approximately 4% combined statistical and systematic uncertainties via a measurement of the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer and forward angle. This will allow an extraction of the weak mixing angle at Q^2=0.026 (GeV/c)^2 to approximately 0.3%. The weak mixing angle is a fundamental parameter in the Standard Model of electroweak interactions. At the proposed accuracy, a measured deviation of this parameter from the predicted value would indicate new physics beyond what is currently described in the Standard Model. Without deviation from the predicted value, this measurement would place stringent limits on possible extensions to the Standard Model and constitute the most precise measurement of the proton's weak charge to date. The key experimental apparatus include a liquid hydrogen target, a toroidal magnetic spectrometer and a set of eight Cerenkov detectors. The Cerenkov detectors form the main detector system for the Q-weak experiment and are used to measure the parity violating asymmetry during the primary Q-weak production runs. The Cerenkov detectors form the main subject of this thesis. Following a brief introduction to the experiment, the design, development, construction, installation, and testing of this detector system will be discussed in detail. This is followed by a detailed discussion of detector diagnostic data analysis and the corresponding detector performance. The experiment has been successfully constructed and commissioned, and is currently taking data. The thesis will conclude with a discussion of the preliminary analysis of a small portion of the liquid hydrogen data.

The goal of the Q-weak experiment is to make a measurement of the proton's weak charge ($Q^p_W = 1-4\sin^2\theta_W$) to an accuracy of ~4%. This would represent a ~0.3% determination of the weak mixing angle ($\sin^2\theta_W$) at low energy. The measurement may be used for a precision test of the Standard Model (SM) prediction on the running of $\sin^2\theta_W$ with energy scale. The Q-weak experiment operates at Thomas Jefferson National Accelerator Facility (Jefferson Lab). The experiment determines the proton's weak charge by measuring the parity violating asymmetry in elastic electron-proton scattering at low momentum transfer $Q^2 = 0.026 (GeV/c)^2$ and forward angles (~8 degree). The anticipated size of the asymmetry, based on the SM, is about 230 parts per billion (ppb). With the proposed accuracy, the experiment may probe new physics beyond Standard Model at the TeV scale. This thesis focuses on my contributions to the experiment, including track reconstruction for momentum transfer determination of the scattering process, and the focal plane scanner, a detector I designed and built to measure the flux profile of scattered electrons on the focal plane of the Q-weak spectrometer to assist in the extrapolation of low beam current tracking results to high beam current. Preliminary results from the commissioning and the first run period of the Q-weak experiment are reported and discussed.

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The Q-weak experiment at Thomas Jefferson National Accelerator Facility (USA) will make a precision determination of the proton weak charge with approximately 4% combined statistical and systematic uncertainties via a measurement of the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer and forward angle. This will allow an extraction of the weak mixing angle at Q^2=0.026 (GeV/c)^2 to approximately 0.3%. The weak mixing angle is a fundamental parameter in the Standard Model of electroweak interactions. At the proposed accuracy, a measured deviation of this parameter from the predicted value would indicate new physics beyond what is currently described in the Standard Model. Without deviation from the predicted value, this measurement would place stringent limits on possible extensions to the Standard Model and constitute the most precise measurement of the proton's weak charge to date. The key experimental apparatus include a liquid hydrogen target, a toroidal magnetic spectrometer and a set of eight Cerenkov detectors. The Cerenkov detectors form the main detector system for the Q-weak experiment and are used to measure the parity violating asymmetry during the primary Q-weak production runs. The Cerenkov detectors form the main subject of this thesis. Following a brief introduction to the experiment, the design, development, construction, installation, and testing of this detector system will be discussed in detail. This is followed by a detailed discussion of detector diagnostic data analysis and the corresponding detector performance. The experiment has been successfully constructed and commissioned, and is currently taking data. The thesis will conclude with a discussion of the preliminary analysis of a small portion of the liquid hydrogen data.

The goal of the Q-weak experiment is to make a measurement of the proton's weak charge ($Q^p_W = 1-4\sin^2\theta_W$) to an accuracy of ~4%. This would represent a ~0.3% determination of the weak mixing angle ($\sin^2\theta_W$) at low energy. The measurement may be used for a precision test of the Standard Model (SM) prediction on the running of $\sin^2\theta_W$ with energy scale. The Q-weak experiment operates at Thomas Jefferson National Accelerator Facility (Jefferson Lab). The experiment determines the proton's weak charge by measuring the parity violating asymmetry in elastic electron-proton scattering at low momentum transfer $Q^2 = 0.026 (GeV/c)^2$ and forward angles (~8 degree). The anticipated size of the asymmetry, based on the SM, is about 230 parts per billion (ppb). With the proposed accuracy, the experiment may probe new physics beyond Standard Model at the TeV scale. This thesis focuses on my contributions to the experiment, including track reconstruction for momentum transfer determination of the scattering process, and the focal plane scanner, a detector I designed and built to measure the flux profile of scattered electrons on the focal plane of the Q-weak spectrometer to assist in the extrapolation of low beam current tracking results to high beam current. Preliminary results from the commissioning and the first run period of the Q-weak experiment are reported and discussed.

Thesis (Ph.D.)--McMaster University (Canada), 1995. / Source: Dissertation Abstracts International, Volume: 57-03, Section: B, page: 2118. Adviser: G. F. Round.

Thesis (Ph.D.); Submitted to Massachusetts Inst. of Tech., Cambridge, MA (US); 1 Sep 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "JLAB-PHY-03-167" "DOE/ER/40150-2745" Marat Rvachev. 09/01/2003. Report is also available in paper and microfiche from NTIS.

Thesis; Thesis information not provided; 1 Feb 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "JLAB-PHY-03-38" "DOE/ER/40150-2762" Bin Zhang. 02/01/2003. Report is also available in paper and microfiche from NTIS.

Si généralement, les variations de sections en travers des rivières naturelles ou anthropisées sont progressives et continues, au droit de certains biefs, des obstacles transversaux et discontinus (naturels ou artificiels) peuvent partiellement ou totalement bloquer les plaines d’inondation. L’écoulement dans la plaine d’inondation est dès lors contracté par l’obstacle, qui promeut le développement de zones de recirculation de part et d’autre de l’obstacle, entraînant une réduction de la section d’écoulement et la génération d’échanges de masse entre lits qui viennent se superposer aux interactions turbulentes. Nous nous sommes intéressés à la modélisation physique de ces écoulements et nous avons particulièrement étudié les distorsions introduites par l’obstacle sur la turbulence dans l’écoulement. Ce travail est basé sur de nouvelles expériences menées dans deux canaux à lit composé. Un jeu complet de données d’écoulements rapidement variés en présence d’un épi dans la plaine d’inondation. Les effets sur les paramètres hydrauliques de la superposition des deux problématiques que sont (i) les écoulements en géométries composées et (ii) les écoulements rapidement variés au voisinage d’un obstacle ont ensuite été analysés. Finalement, les processus physiques dominant dans ces écoulements ont été identifiés / If in natural or anthropized rivers, the river cross-section generally gradually and continuously varies, transversal and discontinuous obstacles either natural or artificial may partially or totally block off floodplains. The flow overbanking in the floodplain is therefore contracted by this obstacle which then promotes two recirculation zones of both sides of the obstacle, resulting in a reduction of the flow section and in the generation of strong mass exchange between channels that superimposes to the classical turbulent interactions. New experiments are conducted in two different compound channels: rapidly varied flows in compound channel with a groyne set on the floodplain. Flows with various groyne lengths and total discharges were investigated. Effects on the hydraulic parameters of the superimposition of the two problems that are (i) flow in compound geometry and (ii) rapidly varied flow in the vicinity of a thin obstacle were analysed. Finally, dominance of physical processes in such flow configuration is discussed

<p>This thesis presents studies of the X-ray linear dichroism (XLD) in individual single-walled (SW) and multi-walled (MW) carbon nanotubes (CNT) measured by a scanning transmission X-ray microscope (STXM). The C 1s spectra of CNT showed a large XLD at the C 1s→π* transition. The magnitude of the XLD was found to be related to the quality of CNT such that in high quality CNT, it was fairly large and as the quality lowered it decreased. This dichroic effect was used to map defects along individual CNT. In addition, STXM was employed to map chemical components in pristine, purified, and dodecyl functionalized SWCNT bundles to investigate the changes occurring in them due to chemical functionalization.<br />STXM has limited spatial resolution. Thus, electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM) was used to obtain similar information about CNT, but at much higher spatial resolution. The measurements performed in the scanning transmission electron microscopy (STEM) mode produced signals analogous to the XLD when the orientation of the momentum transfer (q) was resolved. This was achieved by displacing the pattern of electron scattering from CNT relative to the EELS entrance aperture. TEM-EELS was also utilized to map defects in pristine and focused ion beam (FIB) modified CNT.</p> / Doctor of Philosophy (PhD)