Slotted Rotatable Target Assembley and Systematic Error Analysis for a Search for Long Range Spin Dependent Interactions from Exotic Vector Boson Exchange Using Neutron Spin Rotation

We discuss the design and construction of a novel target array of nonmagnetic test masses used in a neutron polarimetry measurement made in search for new possible exotic spin dependent neutron–atominteractions of Nature at sub-mm length scales. This target was designed to accept and efficiently transmit a transversely polarized slow neutron beam through a series of long open parallel slots bounded by flat rectangular plates. These openings possessed equal atom density gradients normal to the slots from the flat test masses with dimensions optimized to achieve maximum sensitivity to an exotic spin-dependent interaction from vector boson exchanges with ranges in the mm - μm regime. The parallel slots were oriented differently in four quadrants that can be rotated about the neutron beam axis in discrete 90°increments using a Geneva drive. The spin rotation signals from the 4 quadrants were measured using a segmented neutron ion chamber to suppress possible systematic errors from stray magnetic fields in the target region. We discuss the per-neutron sensitivity of the target to the exotic interaction, the design constraints, the potential sources of systematic errors which could be present in this design, and our estimate of the achievable sensitivity using this method

Recent STAR results in high-energy polarized proton-proton collisions at RHIC

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200-500\,$GeV to gain a deeper insight into the spin structure and dynamics of the proton. One of the main objectives of the spin physics program at RHIC is the extraction of the polarized gluon distribution function based on measurements of gluon initiated processes, such as hadron and jet production. The STAR detector is well suited for the reconstruction of various final states involving jets, $\pi^{0}$, $\pi^{\pm}$, e$^{\pm}$ and $\gamma$, which allows to measure several different processes. Recent results will be shown on the measurement of jet production and hadron production at $\sqrt{s}=200\,$GeV. The RHIC spin physics program has recently completed the first data taking period in 2009 of polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=500\,$GeV. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. Recent STAR results on the first measurement of $W$ boson production in polarized $\vec{p}+\vec{p}$ collisions will be shown.Comment: 10 pages, 9 figures, Talk presented at the 26th Winter Workshop on Nuclear Dynamics, Ocho Rios, Jamaica, January 2-9, 2010 to be published in Journal of Physics: Conference Series (JPCS) The author may be contacted via: [email protected]

Global Analysis of Helicity Parton Densities and Their Uncertainties

We present a new analysis of the helicity parton distributions of the nucleon. The analysis takes into account the available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized pp scattering at RHIC. For the first time, all theoretical calculations are performed fully at next-to-leading order (NLO) of perturbative QCD, using a method that allows to incorporate the NLO corrections in a very fast and efficient way in the analysis. We find evidence for a rather small gluon polarization in the nucleon, over a limited region of momentum fraction, and for interesting flavor patterns in the polarized sea.Comment: 4 pages, 3 figure

Recent results from the STAR spin program at RHIC

The STAR experiment uses polarized p+p collisions at RHIC to determine the contributions to the spin of the proton from gluon spin and from orbital angular momentum of the quarks and gluons. Selective STAR measurements of the longitudinal double spin asymmetry for inclusive jet and inclusive hadron production are presented here. In addition, we report measurements of the transverse spin asymmetry for di-jet production at mid-rapidity and the transverse single-spin asymmetry for forward pi0 productionComment: 4 pages, 5 figures, presented at GHP06 conferenc

Measurement of the Absolute np Scattering Differential Cross Section at 194 MeV

We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for np back-scattering to better than 2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle-dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial wave analyses (PWA). The present results are in good accord with the PWA, but deviate systematically from other recent measurements.Comment: 4 pages, 4 figure

Measurement of the Absolute Differential Cross Section for np Elastic Scattering at 194 MeV

A tagged medium-energy neutron beam has been used in a precise measurement of the absolute differential cross section for np back-scattering. The results resolve significant discrepancies within the np database concerning the angular dependence in this regime. The experiment has determined the absolute normalization with 1.5% uncertainty, suitable to verify constraints of supposedly comparable precision that arise from the rest of the database in partial wave analyses. The analysis procedures, especially those associated with evaluation of systematic errors in the experiment, are described in detail so that systematic uncertainties may be included in a reasonable way in subsequent partial wave analysis fits incorporating the present results.Comment: 22 pages, 21 figures, submitted for publication in Physical Review

The Effect of Modern Standard Arabic Orthography on Speech Production by Arab Children With Hearing Loss

This article examined the effect of Modern Standard Arabic orthography on speech production quality (syllable stress and vowels) by 23 Arabic-speaking children with severe or profound hearing loss aged 8–12 years. Children produced 15 one-syllable minimal pairs of words that differed in vowel length (short vs. long) and 20 two-syllable minimal pairs differing in stress pattern. Each word was produced in three tasks: reading partially or fully vowelized words and imitation of aural stimuli. Results showed that fully vowelized words ensured vowel production: high-quality productions appeared on 99%, 74%, and 59% of productions on reading fully vowelized words, partially vowelized words, and on imitation, respectively. Moreover, correct vowel production affected correct consonant production. Correct production of stress was best on reading fully vowelized words, appearing on 54%, 21%, and 33% of productions for fully vowelized words, partially vowelized words, or imitation, respectively. Findings suggest the need to present fully vowelized written texts when teaching speech production to children with hearing loss. Such presentations enable more accurate productions that result in more intelligible speech