We report a measurement of the nuclear polarization of laser-cooled, optically pumped 37K atoms which will allow us to precisely measure angular correlation parameters in the ${\beta }^{+}$-decay of ...the same atoms. These results will be used to test the V ₋ A framework of the weak interaction at high precision. At the Triumf neutral atom trap (Trinat), a magneto-optical trap confines and cools neutral 37K atoms and optical pumping spin-polarizes them. We monitor the nuclear polarization of the same atoms that are decaying in situ by photoionizing a small fraction of the partially polarized atoms and then use the standard optical Bloch equations to model their population distribution. We obtain an average nuclear polarization of $\bar{P}=0.9913\pm 0.0009$, which is significantly more precise than previous measurements with this technique. Since our current measurement of the β-asymmetry has $0.2 \% $ statistical uncertainty, the polarization measurement reported here will not limit its overall uncertainty. This result also demonstrates the capability to measure the polarization to $\lt 0.1 \% $, allowing for a measurement of angular correlation parameters to this level of precision, which would be competitive in searches for new physics.
The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The ...results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.
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We report on precision measurements of the elastic cross section for electron-proton scattering performed in Hall C at Jefferson Lab. The measurements were made at 28 distinct kinematic settings ...covering a range in momentum transfer of 0.4<Q{sup 2}<5.5 (GeV/c){sup 2}. These measurements represent a significant contribution to the world's cross section data set in the Q{sup 2} range, where a large discrepancy currently exists between the ratio of electric to magnetic proton form factors extracted from previous cross section measurements and that recently measured via polarization transfer in Hall A at Jefferson Lab. This data set shows good agreement with previous cross section measurements, indicating that if a heretofore unknown systematic error does exist in the cross section measurements, then it is intrinsic to all such measurements.
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We have extracted QCD matrix elements from our data on doubly polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix element d˜2, which arises strictly from ...quark-gluon interactions, to be unambiguously nonzero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham sum rule is valid. The fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied at our low momentum transfer.
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Inclusive electron-proton and electron-deuteron inelastic cross sections have been measured at Jefferson Lab (JLab) in the resonance region, at large Bjorken x, up to 0.92, and four-momentum transfer ...squared Q{sup 2} up to 7.5 GeV{sup 2} in the experiment E00-116. These measurements are used to extend to larger x and Q{sup 2} precision, quantitative, studies of the phenomenon of quark-hadron duality. Our analysis confirms, both globally and locally, the apparent 'violation' of quark-hadron duality previously observed at a Q{sup 2} of 3.5 GeV{sup 2} when resonance data are compared to structure function data created from CTEQ6M and MRST2004 parton distribution functions (PDFs). More importantly, our new data show that this discrepancy saturates by Q{sup 2}{approx}4 GeV{sup 2}, becoming Q{sup 2} independent. This suggests only small violations of Q{sup 2} evolution by contributions from the higher-twist terms in the resonance region that is confirmed by our comparisons to ALEKHIN and ALLM97. We conclude that the unconstrained strength of the CTEQ6M and MRST2004 PDFs at large x is the major source of the disagreement between data and these parametrizations in the kinematic regime we study and that, in view of quark-hadron duality, properly averaged resonance region data could be used in global quantum chromodynamics fits to reduce PDF uncertainties at large x.
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Subsequent to the release of our original paper, we discovered in the context of preparing our technical supplement 1 for journal publication that a typographical error had existed in the text file ...that the analysis program used to construct the beam polarization "database" for both the original analysis, published in Ref. 2, and our final analysis. The electron-beam polarization Pe and the analyzing power Ay cancel exactly in the ratio R, which is proportional to the ratio Pt/ Pl of the transferred polarization components. On the other hand, the extraction of the relative e dependence of Pl/ PBornl relies on knowledge of the beam polarization. As such, data taking was interrupted roughly every two days during the GEp - 2γ experiment to perform invasive measurements of the beam polarization using the Hall C Moller polarimeter 3.
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We have measured the nuclear transparency of the A(e,e' pi^+) process in ^{2}H,^{12}C, ^{27}Al, ^{63}Cu and ^{197}Au targets. These measurements were performed at the Jefferson Laboratory over a four ...momentum transfer squared range Q^2 = 1.1 - 4.7 (GeV/c)^2. The nuclear transparency was extracted as the super-ratio of $(\sigma_A/\sigma_H)$ from data to a model of pion-electroproduction from nuclei without pi-N final state interactions. The Q^2 and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations, and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.
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Here, this technical note provides supplemental material for the archival publication of the measure- ments of polarization transfer observables in elastic e→p → e→p scattering from the GEp-III and ...GEp-2γ experiments in Jefferson Lab's Hall C.
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The GEp-III and GEp-2γ experiments, carried out in Jefferson Lab’s Hall C from 2007–2008, consisted of measurements of polarization transfer in elastic electron–proton scattering at momentum ...transfers of Q2=2.5,5.2,6.8, and 8.54 GeV 2. These measurements were carried out to improve knowledge of the proton electromagnetic form factor ratio R=μpGEp∕GMp at large values of Q2 and to search for effects beyond the Born approximation in polarization transfer observables at Q2=2.5GeV2. The final results of both experiments were reported in a recent archival publication. A full reanalysis of the data from both experiments was carried out in order to reduce the systematic and, for the GEp-2γ experiment, statistical uncertainties. This technical note provides additional details of the final analysis omitted from the main publication, including the final evaluation of the systematic uncertainties.
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