Publications

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2017
2016
Ibrahim, H., and others, "{Measurements of $d_{2}^{n}$ and $A_{1}^{n}$: Probing the neutron spin structure}", Phys. Rev., vol. D94, no. 5, pp. 052003, 2016. Abstract
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2015
Ibrahim, H., and others, "{E00-110 experiment at Jefferson Lab Hall A: Deeply virtual Compton scattering off the proton at 6 GeV}", Phys. Rev., vol. C92, no. 5, pp. 055202, 2015. Abstract
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Ibrahim, H., and others, "{Moments of the neutron $g_2$ structure function at intermediate $Q^2$}", Phys. Rev., vol. C92, no. 1, pp. 015208, 2015. Abstract
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Ibrahim, H., and others, "{Precision Measurements of $A_1^n$ in the Deep Inelastic Regime}", Phys. Lett., vol. B744, pp. 309-314, 2015. Abstract
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Ibrahim, H., and others, "{Spectroscopy of Lambda-9Li by electroproduction}", Phys. Rev., vol. C91, pp. 034308, 2015. Abstract
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2014
Collaboration, J. L. H. A., "{A Precision Measurement of the Neutron Twist-3 Matrix Element $d_2^n$: Probing Color Forces}", Phys.Rev.Lett., vol. 113, no. 2, pp. 022002, 2014. Abstract

Double-spin asymmetries and absolute cross sections were measured at large Bjorken $x$ (0.25 $ \le x \le $ 0.90), in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized $^3$He target. In this dedicated experiment, the spin structure function $g_2$ on $^3$He was determined with precision at large $x$, and the neutron twist-three matrix element $d_2^n$ was measured at $\left< Q^2\right>$ of 3.21 and 4.32 GeV$^2$/$c^2$, with an absolute precision of about $10^{-5}$. Our results are found to be in agreement with lattice QCD calculations and resolve the disagreement found with previous data at $\left< Q^2\right> =$ 5 GeV$^2$/$c^2$. Combining $d_2^n$ and a newly extracted twist-four matrix element, $f_2^n$, the average neutron color electric and magnetic forces were extracted and found to be of opposite sign and about 30 MeV/fm in magnitude.

Collaboration, J. L. H. A., "{Measurement of double-polarization asymmetries in the quasielastic $^3ěc{\mathrm{He}}(ěc{\mathrm{e}},\mathrm{e}'\mathrm{d})$ process}", Phys.Rev.Lett., vol. 113, no. 23, pp. 232505, 2014. Abstract

We present a precise measurement of double-polarization asymmetries in the He→3(e→,e′d) reaction. This particular process is a uniquely sensitive probe of hadron dynamics in He3 and the structure of the underlying electromagnetic currents. The measurements have been performed in and around quasielastic kinematics at Q2=0.25(GeV/c)2 for missing momenta up to 270  MeV/c. The asymmetries are in fair agreement with the state-of-the-art calculations in terms of their functional dependencies on pm and ω, but are systematically offset. Beyond the region of the quasielastic peak, the discrepancies become even more pronounced. Thus, our measurements have been able to reveal deficiencies in the most sophisticated calculations of the three-body nuclear system, and indicate that further refinement in the treatment of their two-and/or three-body dynamics is required.

Collaboration, J. L. H. A., "{Measurement of pretzelosity asymmetry of charged pion production in Semi-Inclusive Deep Inelastic Scattering on a polarized $^3$He target}", Phys.Rev., vol. C90, no. 5, pp. 055209, 2014. Abstract

An experiment to measure single-spin asymmetries of semi-inclusive production of charged pions in deep-inelastic scattering on a transversely polarized He3 target was performed at Jefferson Laboratory in the kinematic region of 0.16<x<0.35 and 1.4<Q2<2.7GeV2. Pretzelosity asymmetries on He3, which are expressed as the convolution of the h1T⊥ transverse-momentum-dependent distribution functions and the Collins fragmentation functions in the leading order, were measured for the first time. Under the effective polarization approximation, we extracted the corresponding neutron asymmetries from the measured He3 asymmetries and cross-section ratios between the proton and He3. Our results show that both π± on He3 and on neutron pretzelosity asymmetries are consistent with zero within experimental uncertainties.

Collaboration, J. L. H. A., "{Measurement of the $^{12}C(e,e'p)^{11}B$ two-body breakup reaction at high missing momentum}", J.Phys., vol. G41, pp. 105109, 2014. Abstract

The five-fold differential cross section for the (12)C(e,e′p)11B reaction was determined over a missing momentum range of 200–400 MeVc−1, in a kinematics regime with xB>1 and Q2=2.0 (GeVc−1)2. A comparison of the results with previous lower missing momentum data and with theoretical models are presented. The extracted distorted momentum distribution is shown to be consistent with previous data and extends the range of available data up to 400 MeVc−1. The theoretical calculations are from two very different approaches, one mean field and the other short range correlated, yet for this system the two approaches show striking agreement with the data and each other up to a missing momentum value of 325 MeVc−1. For larger momenta, the calculations diverge which is likely due to the factorization approximation used in the short range approach.

Collaboration, J. L. H. A., "{Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction $^{3}\mathrm{He}^{\uparrow}(e,e')X$}", Phys.Rev.Lett., vol. 113, no. 2, pp. 022502, 2014. Abstract

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, $1.02$ 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.

Collaboration, J. L. H. A., "{Single spin asymmetries in charged kaon production from semi-inclusive deep inelastic scattering on a transversely polarized $^3He$ target}", Phys.Rev., vol. C90, no. 5, pp. 055201, 2014. Abstract

We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized $^3{\rm{He}}$ target. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematic range of 0.1$<$$x_{bj}$$<$0.4 for $K^{+}$ and $K^{-}$ production. While the Collins and Sivers moments for $K^{+}$ are consistent with zero within the experimental uncertainties, both moments for $K^{-}$ favor negative values. The Sivers moments are compared to the theoretical prediction from a phenomenological fit to the world data. While the $K^{+}$ Sivers moments are consistent with the prediction, the $K^{-}$ results differ from the prediction at the 2-sigma level.

Collaboration, J. L. H. A., "{Single spin asymmetries of inclusive hadrons produced in electron scattering from a transversely polarized $^3$He target}", Phys.Rev., vol. C89, no. 4, pp. 042201, 2014. Abstract

We report the first measurement of target single-spin asymmetries (A$_N$) in the inclusive hadron production reaction, $e~$+$~^3\text{He}^{\uparrow}\rightarrow h+X$, using a transversely polarized $^3$He target. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons ($\pi^{\pm}$, $\text{K}^{\pm}$ and proton) were detected in the transverse hadron momentum range 0.54 $

2012
2011
Collaboration, J. L. H. A., "{Exclusive Neutral Pion Electroproduction in the Deeply Virtual Regime}", Phys.Rev., vol. C83, pp. 025201, 2011. Abstract
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Collaboration, J. L. H. A., "{Exclusive Neutral Pion Electroproduction in the Deeply Virtual Regime}", Phys.Rev., vol. C83, pp. 025201, 2011. Abstract
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Collaboration, J. L. H. A., "{Low $Q^2$ measurements of the proton form factor ratio $mu_p G_E / G_M$}", Phys.Rev., vol. C84, pp. 055204, 2011. Abstract
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Collaboration, J. L. H. A., "{Low $Q^2$ measurements of the proton form factor ratio $mu_p G_E / G_M$}", Phys.Rev., vol. C84, pp. 055204, 2011. Abstract
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Collaboration, J. L. H. A., "{Probing the high momentum component of the deuteron at high Q^2}", Phys.Rev.Lett., vol. 107, pp. 262501, 2011. Abstract
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2009
Collaboration, J. L. H. A., "{High Resolution Spectroscopy of N-16(Lambda) by Electroproduction}", Phys.Rev.Lett., vol. 103, pp. 202501, 2009. Abstract
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Collaboration, J. L. H. A., "{High Resolution Spectroscopy of N-16(Lambda) by Electroproduction}", Phys.Rev.Lett., vol. 103, pp. 202501, 2009. Abstract
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2008
Collaboration, J. L. H. A., "{Probing Cold Dense Nuclear Matter}", Science, vol. 320, pp. 1476-1478, 2008. Abstract
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Collaboration, J. L. H. A., "{Probing Cold Dense Nuclear Matter}", Science, vol. 320, pp. 1476-1478, 2008. Abstract
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Collaboration, J. L. H. A., "{Quark-Hadron Duality in Neutron (He-3) Spin Structure}", Phys.Rev.Lett., vol. 101, pp. 182502, 2008. Abstract
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Collaboration, J. L. H. A., "{Quark-Hadron Duality in Neutron (He-3) Spin Structure}", Phys.Rev.Lett., vol. 101, pp. 182502, 2008. Abstract
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2007
Collaboration, J. L. H. A., "{Deeply virtual compton scattering off the neutron}", Phys.Rev.Lett., vol. 99, pp. 242501, 2007. Abstract
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Collaboration, J. L. H. A., "{Deeply virtual compton scattering off the neutron}", Phys.Rev.Lett., vol. 99, pp. 242501, 2007. Abstract
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Collaboration, J. L. H. A., "{High Resolution Spectroscopy of B-12(Lambda) by Electroproduction}", Phys.Rev.Lett., vol. 99, pp. 052501, 2007. Abstract
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Collaboration, J. L. H. A., "{High Resolution Spectroscopy of B-12(Lambda) by Electroproduction}", Phys.Rev.Lett., vol. 99, pp. 052501, 2007. Abstract
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Collaboration, J. L. H. A., "{Investigation of proton-proton short-range correlations via the C-12(e, e-prime pp) reaction}", Phys.Rev.Lett., vol. 99, pp. 072501, 2007. Abstract
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Collaboration, J. L. H. A., "{Precision Measurements of the Nucleon Strange Form Factors at Q**2   0.1-GeV**2}", Phys.Rev.Lett., vol. 98, pp. 032301, 2007. Abstract
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Collaboration, J. L. H. A., "{Precision Measurements of the Nucleon Strange Form Factors at Q**2   0.1-GeV**2}", Phys.Rev.Lett., vol. 98, pp. 032301, 2007. Abstract
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Acha, A., and others, "{Precision Measurements of the Nucleon Strange Form Factors at Q**2   0.1-GeV**2}", Phys. Rev. Lett., vol. 98, pp. 032301, 2007. Abstract
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