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Search Results: 1 - 10 of 23649 matches for " Paul Souder "
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Weak Polarized Electron Scattering
Jens Erler,Charles J. Horowitz,Sonny Mantry,Paul A. Souder
Physics , 2014, DOI: 10.1146/annurev-nucl-102313-025520
Abstract: Scattering polarized electrons provides an important probe of the weak interactions. Precisely measuring the parity-violating left-right cross section asymmetry is the goal of a number of experiments recently completed or in progress. The experiments are challenging, since A_{LR} is small, typically between 10^(-4) and 10^(-8). By carefully choosing appropriate targets and kinematics, various pieces of the weak Lagrangian can be isolated, providing a search for physics beyond the Standard Model. For other choices, unique features of the strong interaction are studied, including the radius of the neutron density in heavy nuclei, charge symmetry violation, and higher twist terms. This article reviews the theory behind the experiments, as well as the general techniques used in the experimental program.
The Pupil of the People: Lev Nikolaevich Tolstoy's Peasant Schools at Yasnaya Polyana
Eric M. Souder
Vestnik : The Journal of Russian and Asian Studies , 2010,
Abstract: In the late 1850s, Tolstoy began investigating popular education, as well as contemplating the establishment of his own peasant schools on his Yasnaya Polyana estate. At the turn of the decade, Tolstoy founded his school.[6] While this venture lasted only about three years, it represented the concerted effort of one of the world's most famous literary figures to alter the state of Russia's educational system. Furthermore, this event illustrates the multifaceted nature of Tolstoy himself; even in this early stage of Tolstoy's literary career, he shows signs of radical dissent from the established order in the desire to improve Russian society.
Measuring the weak mixing angle with the P2 experiment at MESA
Niklaus Berger,Kurt Aulenbacher,Sebastian Baunack,Dominik Becker,Jürgen Diefenbach,Michael Gericke,Kathrin Gerz,Ruth Herbertz,Krishna Kumar,Frank Maas,Matthias Molitor,David Rodríguez Pi?eiro,Iurii Sorokin,Paul Souder,Hubert Spiesberger,Alexey Tyukin,Valery Tyukin,Marco Zimmermann
Physics , 2015,
Abstract: The P2 experiment in Mainz aims to measure the weak mixing angle in electron- proton scattering to a precision of 0.13 %. In order to suppress uncertainties due to proton structure and contributions from box graphs, both a low average momentum transfer $Q^2$ of $4.5\cdot 10^{-3}$ GeV$^2/c^2$ and a low beam energy of 155 MeV are chosen. In order to collect the enormous statistics required for this measurement, the new Mainz Energy Recovery Superconducting Accelerator (MESA) is being constructed. These proceedings describe the motivation for the measurement, the experimental and accelerator challenges and how we plan to tackle them.
Development of an instrument to measure the quality of standardized/simulated patient verbal feedback
Win May,Dixie Fisher,Denise Souder
Medical Education Development , 2012, DOI: 10.4081/med.2012.e3
Abstract: Standardized/simulated patients (SPs) are being asked to provide formative verbal feedback to medical students. There is a need to objectively measure the quality of this feedback. This paper describes the theoretical and empirical development of the Quality of Standardized Patient Feedback form (QSF), an instrument designed to measure the quality of standardized/simulated patient verbal feedback. The QSF consists of 7 categories derived from existing literature on feedback. Interrater and internal consistency reliabilities of QSF scores were calculated through two pilot studies. In the first, 2 standardized patient educators (SPEs) analyzed 14 videos of SP verbal feedback (weighted kappa = 0.73). In the second study, 14 SPs rated 3 videos (Intraclass correlation coefficient = 0.92. Internal reliability was 0.79 (Cronbach’s alpha). Twenty-one expert SPEs were asked to rate the QSF categories as to their importance in providing feedback to learners. SPEs agreed on the importance of five of the seven categories, but were split on the importance of two categories. We found theoretical and practical support for the QSF categories. The QSF is a useful instrument for evaluating the quality of SP verbal feedback.
Target Cell Availability, Rather than Breast Milk Factors, Dictates Mother-to-Infant Transmission of SIV in Sooty Mangabeys and Rhesus Macaques
Ann Chahroudi ,Emily Cartwright,S. Thera Lee,Maud Mavigner,Diane G. Carnathan,Benton Lawson,Paul M. Carnathan,Tayebeh Hashempoor,Megan K. Murphy,Tracy Meeker,Stephanie Ehnert,Christopher Souder,James G. Else,Joyce Cohen,Ronald G. Collman,Thomas H. Vanderford,Sallie R. Permar,Cynthia A. Derdeyn,Francois Villinger,Guido Silvestri
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1003958
Abstract: Mother-to-infant transmission (MTIT) of HIV is a serious global health concern, with over 300,000 children newly infected in 2011. SIV infection of rhesus macaques (RMs) results in similar rates of MTIT to that of HIV in humans. In contrast, SIV infection of sooty mangabeys (SMs) rarely results in MTIT. The mechanisms underlying protection from MTIT in SMs are unknown. In this study we tested the hypotheses that breast milk factors and/or target cell availability dictate the rate of MTIT in RMs (transmitters) and SMs (non-transmitters). We measured viral loads (cell-free and cell-associated), levels of immune mediators, and the ability to inhibit SIV infection in vitro in milk obtained from lactating RMs and SMs. In addition, we assessed the levels of target cells (CD4+CCR5+ T cells) in gastrointestinal and lymphoid tissues, including those relevant to breastfeeding transmission, as well as peripheral blood from uninfected RM and SM infants. We found that frequently-transmitting RMs did not have higher levels of cell-free or cell-associated viral loads in milk compared to rarely-transmitting SMs. Milk from both RMs and SMs moderately inhibited in vitro SIV infection, and presence of the examined immune mediators in these two species did not readily explain the differential rates of transmission. Importantly, we found that the percentage of CD4+CCR5+ T cells was significantly lower in all tissues in infant SMs as compared to infant RMs despite robust levels of CD4+ T cell proliferation in both species. The difference between the frequently-transmitting RMs and rarely-transmitting SMs was most pronounced in CD4+ memory T cells in the spleen, jejunum, and colon as well as in central and effector memory CD4+ T cells in the peripheral blood. We propose that limited availability of SIV target cells in infant SMs represents a key evolutionary adaptation to reduce the risk of MTIT in SIV-infected SMs.
Low Energy Measurements of the Weak Mixing Angle
Kumar, K. S.;Mantry, Sonny;Marciano, W. J.;Souder, P. A.
High Energy Physics - Phenomenology , 2013,
Abstract: We review the status of precision measurements of weak neutral current interactions, mediated by the $Z^0$ boson, at $Q^2\ll M_Z^2$. They can be used to extract values for the weak mixing angle $\sin^2\theta_W$, a fundamental parameter of the $SU(2)_L\times U(1)_Y$ electroweak sector of the Standard Model. Apart from providing a comprehensive test of the electroweak theory at the quantum loop level, such measurements allow indirect access to new physics effects at and beyond the TeV scale. After a theoretical introduction and a brief overview of the three most precise low $Q^2$ weak mixing angle determinations, we describe the ongoing experimental program and prospects for future more sensitive studies. We also compare sensitivities of planned and proposed measurements to physics beyond the Standard Model.
Preliminary Results from Integrating Compton Photon Polarimetry in Hall A of Jefferson Lab
D. Parno,M. Friend,F. Benmokhtar,G. Franklin,R. Michaels,S. Nanda,B. Quinn,P. Souder
Physics , 2011, DOI: 10.1088/1742-6596/312/5/052018
Abstract: A wide range of nucleon and nuclear structure experiments in Jefferson Lab's Hall A require precise, continuous measurements of the polarization of the electron beam. In our Compton polarimeter, electrons are scattered off photons in a Fabry-Perot cavity; by measuring an asymmetry in the integrated signal of the scattered photons detected in a GSO crystal, we can make non-invasive, continuous measurements of the beam polarization. Our goal is to achieve 1% statistical error within two hours of running. We discuss the design and commissioning of an upgrade to this apparatus, and report preliminary results for experiments conducted at beam energies from 3.5 to 5.9 GeV and photon rates from 5 to 100 kHz.
Low Energy Measurements of the Weak Mixing Angle
K. S. Kumar,Sonny Mantry,W. J. Marciano,P. A. Souder
Physics , 2013, DOI: 10.1146/annurev-nucl-102212-170556
Abstract: We review the status of precision measurements of weak neutral current interactions, mediated by the $Z^0$ boson, at $Q^2\ll M_Z^2$. They can be used to extract values for the weak mixing angle $\sin^2\theta_W$, a fundamental parameter of the $SU(2)_L\times U(1)_Y$ electroweak sector of the Standard Model. Apart from providing a comprehensive test of the electroweak theory at the quantum loop level, such measurements allow indirect access to new physics effects at and beyond the TeV scale. After a theoretical introduction and a brief overview of the three most precise low $Q^2$ weak mixing angle determinations, we describe the ongoing experimental program and prospects for future more sensitive studies. We also compare sensitivities of planned and proposed measurements to physics beyond the Standard Model.
Parity Violating Measurements of Neutron Densities
C. J. Horowitz,S. J. Pollock,P. A. Souder,R. Michaels
Physics , 1999, DOI: 10.1103/PhysRevC.63.025501
Abstract: Parity violating electron nucleus scattering is a clean and powerful tool for measuring the spatial distributions of neutrons in nuclei with unprecedented accuracy. Parity violation arises from the interference of electromagnetic and weak neutral amplitudes, and the $Z^0$ of the Standard Model couples primarily to neutrons at low $Q^2$. The data can be interpreted with as much confidence as electromagnetic scattering. After briefly reviewing the present theoretical and experimental knowledge of neutron densities, we discuss possible parity violation measurements, their theoretical interpretation, and applications. The experiments are feasible at existing facilities. We show that theoretical corrections are either small or well understood, which makes the interpretation clean. The quantitative relationship to atomic parity nonconservation observables is examined, and we show that the electron scattering asymmetries can be directly applied to atomic PNC because the observables have approximately the same dependence on nuclear shape.
A White Paper on SoLID (Solenoidal Large Intensity Device)
J. P. Chen,H. Gao,T. K. Hemmick,Z. -E. Meziani,P. A. Souder,the SoLID Collaboration
Physics , 2014,
Abstract: In order to fully exploit the physics potential of Jefferson Lab after 12 GeV energy upgrade, a new Solenoidal Large Acceptance Device (SoLID) is proposed. The SoLID spectrometer, with its unique capability of large acceptance and high luminosity, is ideal for precision measurements in semi-inclusive DIS to study transverse spin and transverse-momentum-dependent parton distributions of the nucleon, and for parity-violating Deep Inelastic Scattering (DIS) to perform precision tests of the Standard Model at low energy as well as addressing specific issues in nucleon structure including charge symmetry violation, d/u ratio and higher-twist effects due to di-quark. SoLID is also essential for precision measurements of J/\psi electroproduction in the threshold region to study non-perturbative gluon dynamics and interaction. Five highly rated SoLID experiments and two "run group" experiments have been approved by the JLab Physics Advisory Committee. The physics program is presented along with an overview of the SoLID instrumentation and its current status.
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