A SIGNATURE FOR ISOSCALAR-SPIN TRANSITIONS IN ([d,d) SCATTERING

Three different signatures for isoscalar spin transitions in nuclei have been tested in the 12C(d,d)12C reaction at 400 MeV. These signatures have values close to zero for the natural parity states, and ranging from 0.22 to 0.50 for the ΔS=1 ΔT=0, 12.7 MeV state

Quark-Hadron Duality in Neutron (3He) Spin Structure

We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_1 of the neutron and $^3$He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and found no strong Q^2-dependence above 2.2 (GeV/c)^2.Comment: 13 pages, 3 figure

Polarization transfer in the 4^{4}He(e⃗,e′p⃗3(\vec{e},e' \vec{p}^{3}H reaction

Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.Comment: 5 pages, Latex, 2 postscript figures, submitted to Physics Letters

Polarization transfer in the d(epol,e' ppol)n reaction up to Q^2=1.61 (GeV/c)^2

The recoil proton polarization was measured in the d(epol,e' ppol)n reaction in Hall A of the Thomas Jefferson National Accelerator Facility (JLab). The electron kinematics were centered on the quasielastic peak (x_{Bj}~1) and included three values of the squared four-momentum transfer, Q^2=0.43, 1.00 and 1.61 (GeV/c)^2. For Q^2=0.43 and 1.61 (GeV/c)^2, the missing momentum, p_m, was centered at zero while for Q^2=1.00 (GeV/c)^2 two values of p_m were chosen: 0 and 174 MeV/c. At low p_m, the Q^2 dependence of the longitudinal polarization, P_z', is not well described by a state-of-the-art calculation. Further, at higher p_m, a 3.5 sigma discrepancy was observed in the transverse polarization, P_x'. Understanding the origin of these discrepancies is important in order to confidently extract the neutron electric form factor from the analogous d(epol,e' npol)p experiment.Comment: 6 pages, 4 figures; updated text, figures and table

Moments of the neutron g2g_2 structure function at intermediate Q2Q^2

We present new experimental results of the $^3$He spin structure function $g_2$ in the resonance region at $Q^2$ values between 1.2 and 3.0 (GeV/c)$^2$. Spin dependent moments of the neutron were then extracted. Our main result, the resonance contribution to the neutron $d_2$ matrix element, was found to be small at $$=2.4 (GeV/c)$^2$ and in agreement with the Lattice QCD calculation. The Burkhardt-Cottingham sum rule for $^3$He and the neutron was tested with the measured data and using the Wandzura-Wilczek relation for the low $x$ unmeasured region. A small deviation was observed at $Q^2$ values between 0.5 and 1.2 (GeV/c)$^2$ for the neutron

Measurement of the Generalized Forward Spin Polarizabilities of the Neutron

The generalized forward spin polarizabilities $\gamma_0$ and $\delta_{LT}$ of the neutron have been extracted for the first time in a $Q^2$ range from 0.1 to 0.9 GeV$^2$. Since $\gamma_0$ is sensitive to nucleon resonances and $\delta_{LT}$ is insensitive to the $\Delta$ resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on $\delta_{LT}$ show significant disagreement with Chiral Perturbation Theory calculations, while the data for $\gamma_0$ at low $Q^2$ are in good agreement with a next-to-lead order Relativistic Baryon Chiral Perturbation theory calculation. The data show good agreement with the phenomenological MAID model.Comment: 5 pages, 2 figures, corrected typo in author name, published in PR

Recoil Polarization Measurements for Neutral Pion Electroproduction at Q^2=1 (GeV/c)^2 Near the Delta Resonance

We measured angular distributions of differential cross section, beam analyzing power, and recoil polarization for neutral pion electroproduction at Q^2 = 1.0 (GeV/c)^2 in 10 bins of W across the Delta resonance. A total of 16 independent response functions were extracted, of which 12 were observed for the first time. Comparisons with recent model calculations show that response functions governed by real parts of interference products are determined relatively well near 1.232 GeV, but variations among models is large for response functions governed by imaginary parts and for both increases rapidly with W. We performed a nearly model-independent multipole analysis that adjusts complex multipoles with high partial waves constrained by baseline models. Parabolic fits to the W dependence of the multipole analysis around the Delta mass gives values for SMR = (-6.61 +/- 0.18)% and EMR = (-2.87 +/- 0.19)% that are distinctly larger than those from Legendre analysis of the same data. Similarly, the multipole analysis gives Re(S0+/M1+) = (+7.1 +/- 0.8)% at W=1.232 GeV, consistent with recent models, while the traditional Legendre analysis gives the opposite sign because its truncation errors are quite severe. Finally, using a unitary isobar model (UIM), we find that excitation of the Roper resonance is dominantly longitudinal with S1/2 = (0.05 +/- 0.01) GeV^(-1/2) at Q^2=1. The ReS0+ and ReE0+ multipoles favor pseudovector coupling over pseudoscalar coupling or a recently proposed mixed-coupling scheme, but the UIM does not reproduce the imaginary parts of 0+ multipoles well.Comment: 60 pages, 54 figure

The Q^2 evolution of the generalized Gerasimov-Drell-Hearn integral for the neutron using a He-3 target

We present data on the inclusive scattering of polarized electrons from a polarized He-3 target at energies from 0.862 to 5.06 GeV, obtained at a scattering angle of 15.5 degrees. Our data include measurements from the quasielastic peak, through the resonance region, to the beginning of the deep inelastic regime, and were used to determine the spin difference in the virtual photoabsorption cross section. We extract the extended Gerasimov-Drell-Hearn integral for the neutron in the range of 4-momentum transfer squared Q^2 of 0.1-0.9 GeV.Comment: 14 pages of text when TeXed in preprint format with figures embedded. RevTeX format. Three eps figure

Phenomenology of the Deuteron Electromagnetic Form Factors

A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm^-1. This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data.Comment: 18 pages (LaTeX), 2 figures Feb. 25: minor changes of content and in Table

Q^2 Evolution of the Neutron Spin Structure Moments using a He-3 Target

We have measured the spin structure functions $g_1$ and $g_2$ of $^3$He in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.07 GeV off a polarized $^3$He target at a 15.5$^{\circ}$ scattering angle. Excitation energies covered the resonance and the onset of the deep inelastic regions. We have determined for the first time the $Q^2$ evolution of $\Gamma_1(Q^2)=\int_0^{1} g_1(x,Q^2) dx$, $\Gamma_2(Q^2)=\int_0^1 g_2(x,Q^2) dx$ and $d_2 (Q^2) = \int_0^1 x^2[ 2g_1(x,Q^2) + 3g_2(x,Q^2)] dx$ for the neutron in the range 0.1 GeV$^2$ $\leq Q^2 \leq$ 0.9 GeV$^2$ with good precision. $\Gamma_1(Q^2)$ displays a smooth variation from high to low $Q^2$. The Burkhardt-Cottingham sum rule holds within uncertainties and $d_2$ is non-zero over the measured range.Comment: 5 pages, 2 figures, submitted to Phys. Rev. Lett.. Updated Hermes data in Fig. 2 (top panel) and their corresponding reference. Updated the low x extrapolation error Fig. 2 (middle panel). Corrected references to ChiPT calculation