Elastic scattering of longitudinally polarized electrons from helium-4: A measurement of G(E)(S) at Q2 = 0.1 (GeV/c)2

We have performed the first measurement of the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons from 4He. The kinematics chosen (Q 2 = 0.1 (GeV/c)2) provide a direct sensitivity to the strange electric form factor GsE with negligible contributions from competing effects. This experiment was performed in June 2004 and July-September 2005 in Hall A at Jefferson Lab. This work represents the experimental setup and analysis of the 2004 dataset.;The final statistical precision, from the combined datasets, put stringent requirements on the systematic errors that normalize the asymmetry (e.g. Q2, beam polarization, backgrounds). The experimental and analysis techniques, presented in this thesis, resulted in a 12.9% relative measure of the parity-violating asymmetry for the 2004 dataset, and a 4.1% relative measure for the 2005 dataset (the most precise measurement of a parity-violating asymmetry ever obtained).;The 2004 measured result, APV = 6.72 +/- 0.84 (stat) +/- 0.21 (syst) ppm, allows for the extraction of the electric strange form factor: GsE (Q2 = 0.1) = -0.038 +/- 0.042 (stat) +/- 0.010 (syst). When combined with results from previous experiments, at nearly the same kinematics, a clear picture of the contribution of strange quarks to the nucleon\u27s electric and magnetic form factors emerges

Precision measurements of A1N in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A1A1 on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized 3He target. Our data cover a wide kinematic range 0.277≤x≤0.5480.277≤x≤0.548 at an average Q2Q2 value of 3.078 (GeV/c)2, doubling the available high-precision neutron data in this x range. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of anA1n zero crossing near x=0.5x=0.5. We find no evidence of a transition to a positive slope in(Δd+Δd¯)/(d+d¯) up to x=0.548x=0.548

Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction 3He↑(e,e′)X^{3}\mathrm{He}^{\uparrow}(e,e')X

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction $^3$He$^{\uparrow}\left(e,e' \right)X$ on a polarized $^3$He gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be non-zero if two-photon-exchange contributions are included. The experiment, conducted at Jefferson Lab using a 5.89 GeV electron beam, covers a range of $1.7 < W < 2.9$ GeV, $1.0<Q^2<4.0$ GeV$^2$ and $0.16<x<0.65$. Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to-$^3$He cross section ratios. The measured neutron asymmetries are negative with an average value of $(-1.09 \pm 0.38) \times10^{-2}$ for invariant mass $W>2$ GeV, which is non-zero at the $2.89\sigma$ level. Our measured asymmetry agrees both in sign and magnitude with a two-photon-exchange model prediction that uses input from the Sivers transverse momentum distribution obtained from semi-inclusive deep-inelastic scattering.Comment: This is the final edited version as published in PR

Precision measurements of A[n over 1] in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A[subscript 1] on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized [superscript 3]He target. Our data cover a wide kinematic range 0.277 ≤ x ≤ 0.548 at an average Q[superscript 2] value of 3.078 (GeV/c)[superscript 2], doubling the available high-precision neutron data in this x range. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of an A[n over 1] zero crossing near x = 0.5. We find no evidence of a transition to a positive slope in (Δd + Δ[bar over d])/(d + [bar over d]) up to x = 0.548

Single spin asymmetries of inclusive hadrons produced in electron scattering from a transversely polarized [superscript 3]He target

We report the first measurement of target single spin asymmetries (A[subscript N]) in the inclusive hadron production reaction, e + [superscript 3]He[superscript ↑] → h + X, using a transversely polarized [superscript 3]He target. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons (π[superscript ±], K[superscript ±], and proton) were detected in the transverse hadron momentum range 0.54 < p[subscript T] < 0.74 GeV/c. The range of x[subscript F] for pions was −0.29 < x[subscript F] < −0.23 and for kaons was −0.25 < x[subscript F] < −0.18. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π[superscript +] and K[superscript +]. A negative asymmetry is observed for π[superscript −]. The magnitudes of the asymmetries follow ∣∣A[superscript π−] |<| A[superscript π+] |<| A[superscript K+]∣∣. The K[superscript −] and proton asymmetries are consistent with zero within the experimental uncertainties. The π[superscript +] and π[superscript −] asymmetries measured for the [superscript 3]He target and extracted for neutrons are opposite in sign with a small increase observed as a function of p[subscript T].National Science Foundation (U.S.)United States. Dept. of Energy (Contract DE-AC05-06OR23177

Constraining timing of brittle deformation and fault gouge formation in the Sydney Basin

Structural and K–Ar dating studies of gouge in N–S, NNE and E–W-trending faults in four locations in the Sydney–Hunter region are reported. The fault zones are manifest as joint swarms and highly brecciated zones containing gouge with authigenic illite produced as a result of fluid infiltration. Strike-slip movement accompanied by minor dip-slip, normal movement occurred on the NNE faults, with dip slip on N–S and E–W-trending faults. In this study, gouge from a NE-trending, steep, SE-dipping fault showing dip-slip movement at Cut 10, on the Hunter Expressway and from an E–W-trending, steep south-dipping, normal fault at the Westside Open Cut, Lake Macquarie have been analysed. K–Ar dating of illite and illite–smectite in fractions extracted from fault gouges in areas unaffected by a thermal overprint reveals ages varying from 166 to 119 Ma for the <2 μm and finer fractions, and a mean age of ca 120 Ma for the <0.4 μm fraction. In the Sydney area and the Westside Open Cut coal mine, Lake Macquarie, the ages obtained from similar size fractions both for the gouge and for the host rocks are younger (134–76 Ma; av. <0.4 μm = 111 Ma). The data indicate influence of a thermal overprint associated with subsurface magmas emplaced during the early stages of the rifting of eastern Gondwana during the early Cretaceous

Measurement of the generalized spin polarizabilities of the neutron in the low-Q2Q^2 region

International audienceUnderstanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques such as chiral effective field theory1. Here we present measurements of the neutron’s generalized spin polarizabilities that quantify the neutron’s spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV2. In this regime, chiral effective field theory calculations2,3,4 are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron’s spin properties