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

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction ^3He^↑ (e,e′) X on a polarized ^3He gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero 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 2  GeV, which is nonzero at the 2.89σ 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

Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction ³He↑(e,e\u27)X

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction 3He↑(e, e\u27)X on a polarized 3He gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero 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 \u3c W \u3c 2.9 GeV, 1.0 \u3c Q2 \u3c 4.0 GeV2 and 0.16 \u3c x \u3c 0.65. Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to-3He cross-section ratios. The measured neutron asymmetries are negative with an average value of (-1.09 ± 0.38) x 10-2for invariant mass W \u3e 2 GeV, which is nonzero at the 2.89σ 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

Precision Measurement of the Neutron Twist-3 Matrix Element d(2)(n): Probing Color Forces

Double-spin asymmetries and absolute cross sections were measured at large Bjorken x (0.25 of 3.21 and 4.32 GeV2/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 \u3c Q(2)\u3e = 5 GeV2/c(2). Combining d(2)(n) and a newly extracted twist-4 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

Beam-Target Double-Spin Asymmetry A(LT) in Charged Pion Production from Deep Inelastic Scattering on a Transversely Polarized He-3 Target at 1.4 \u3c Q(2) \u3c 2.7 GeV2

We report the first measurement of the double-spin asymmetry A(LT) for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized He-3 target. The kinematics focused on the valence quark region, 0.16 \u3c x \u3c 0.35 with 1.4 \u3c Q(2) \u3c 2.7 GeV2. The corresponding neutron A(LT) asymmetries were extracted from the measured He-3 asymmetries and proton over He-3 cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g(1T)(q) and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for pi(-) production on He-3 and the neutron, while our pi(+) asymmetries are consistent with zero

Measurement of Double-Polarization Asymmetries in the Quasielastic (3)(He)over-right-arrow((e)over-right-arrow,e \u27 d) Process

We present a precise measurement of double-polarization asymmetries in the (3)(He) over right arrow((e) over right arrow ,e\u27d) reaction. This particular process is a uniquely sensitive probe of hadron dynamics in He-3 and the structure of the underlying electromagnetic currents. The measurements have been performed in and around quasielastic kinematics at Q(2) = 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 p(m) and omega, 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

Double spin asymmetries of inclusive hadron electroproduction from a transversely polarized He-3 target

We report the measurement of beam-target double spin asymmetries (A(LT)) in the inclusive production of identified hadrons, (e) over right arrow + 3He(up arrow) -\u3e h + X, using a longitudinally polarized 5.9-GeV electron beam and a transversely polarized He-3 target. Hadrons (pi(+/-), K-+/-, and proton) were detected at 16 degrees with an average momentum \u3c Ph \u3e = 2.35 GeV/c and a transverse momentum (p(T)) coverage from 0.60 to 0.68 GeV/c. Asymmetries from the He-3 target were observed to be nonzero for pi(+/-) production when the target was polarized transversely in the horizontal plane. The pi(+) and pi(-) asymmetries have opposite signs, analogous to the behavior of A(LT) in semi-inclusive deep-inelastic scattering

Single spin asymmetries in charged kaon production from semi-inclusive deep inelastic scattering on a transversely polarized He-3 target

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 He-3 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 \u3c x(bj) \u3c 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

Measurements of d(2)(n) and A(1)(n) : Probing the neutron spin structure

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d(2) of the neutron (d(2)(n)) was conducted. The quantity d(2)(n) represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the He-3 spin structure functions, g(1) and g(2), after nuclear corrections had been applied to these moments. The structure functions were obtained from a measurement of the unpolarized cross section and of double-spin asymmetries in the scattering of a longitudinally polarized electron beam from a transversely and a longitudinally polarized He-3 target. The measurement kinematics included two average Q(2) bins of 3.2 GeV2 and 4.3 GeV2, and Bjorken-x 0.25 = 3.2 GeV2, and even smaller for \u3c Q(2)\u3e = 4.3 GeV2, consistent with the results of a lattice QCD calculation. The twist-4 matrix element f(2)(n) was extracted by combining our measured d(2)(n) with the world data on the first moment in x of g(1)(n), Gamma(n)(1). We found f(2)(n) to be roughly an order of magnitude larger than d(2)(n). Utilizing the extracted d(2)(n) and f(2)(n) data, we separated the Lorentz color force into its electric and magnetic components, F-E(y,n) and F-B(y,n), and found them to be equal and opposite in magnitude, in agreement with the predictions from an instanton model but not with those from QCD sum rules. Furthermore, using the measured double-spin asymmetries, we have extracted the virtual photon-nucleon asymmetry on the neutron A(1)(n), the structure function ratio g(1)(n)/F-1(n), and the quark ratios (Delta u + Delta(u) over bar)/(u + (u) over bar) and (Delta d + Delta(d) over bar)/(d + (d) over bar). These results were found to be consistent with deep-inelastic scattering world data and with the prediction of the constituent quark model but at odds with the perturbative quantum chromodynamics predictions at large x

Precision measurements of A(1)(n) in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A(1) on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized He-3 target. Our data cover a wide kinematic range 0.277 \u3c = x \u3c = 0.548 at an average Q(2) value of 3.078(GeV/c)(2), doubling the available high-precision neutron data in this xrange. 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(1)(n) zero crossing near x = 0.5. We find no evidence of a transition to a positive slope in (Delta d + Delta(d) over bar)/(d + (d) over bar) up to x = 0.548. (C) 2015 The Authors. Published by Elsevier B.V

Measurement of pretzelosity asymmetry of charged pion production in semi-inclusive deep inelastic scattering on a polarized He-3 target

An experiment to measure single-spin asymmetries of semi-inclusive production of charged pions in deep-inelastic scattering on a transversely polarized He-3 target was performed at Jefferson Laboratory in the kinematic region of 0.16 \u3c x \u3c 0.35 and 1.4 \u3c Q(2) \u3c 2.7 GeV2. Pretzelosity asymmetries on He-3, which are expressed as the convolution of the h(1T)(perpendicular to) 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 He-3 asymmetries and cross-section ratios between the proton and He-3. Our results show that both pi(+) on He-3 and on neutron pretzelosity asymmetries are consistent with zero within experimental uncertainties