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Register a new userThe Double Spin Asymmetry of Nitrogen in Elastic and Quasielastic Kinematics from a Solid Ammonia Dynamically Polarized Target
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Solid ammonia (NH$_3$) is commonly used as a dynamically polarized proton target for electron and muon scattering cross-section asymmetry measurements. As spin 1$^{+}$ particles, the $^{14}$N nuclei in the target are also polarized and contribute a non-trivial asymmetry background that should be addressed. We describe here a method to extract the nitrogen contribution to the asymmetry, and report the cross-section asymmetries of electron-nitrogen scattering at beam energies of $E=1.7$ GeV and $E=2.2$ GeV, and momentum transfer of $Q^{2}=0.023-0.080$ GeV$^{2}$.
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Quasi-elastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D-state admixture) and on the limits of the Impulse Approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. We measured the beam-target double spin asymmetry for quasi-elastic electron scattering off the deuteron at several beam energies using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double spin asymmetries were measured as a function of photon virtuality , missing momentum, and the angle between the (inferred) spectator neutron and the momentum transfer direction. The results are compared with a recent model that includes Final State Interactions (FSI) using a complete parameterization of nucleon-nucleon scattering, as well as a simplified model using the Plane Wave Impulse Approximation (PWIA). We find overall good agreement with both the PWIA and FSI expectations at low to medium missing momenta, including the change of the asymmetry due to the contribution of the deuteron D-state at higher momenta. At the highest missing momenta, our data clearly agree better with the calculations including FSI.
Precise measurements of the single spin asymmetry, $A_N$ and the double spin asymmetry, $A_{NN}$, in proton-proton (textit{pp}) elastic scattering in the region of four-momentum transfer squared $0.001 < -t < 0.032 ({rm GeV}/c)^2$ have been performed using a polarized atomic hydrogen gas jet target and the RHIC polarized proton beam at 24 GeV/$c$ and 100 GeV/$c$. The polarized gaseous proton target allowed us to achieve the measurement of $A_{NN}$ in the CNI region for the first time. Our results of $A_N$ and $A_{NN}$ provide significant constraints to determine the magnitude of poorly known hadronic single and double spin-flip amplitudes at this energy.
We report the measurement of beam-target double-spin asymmetries ($A_text{LT}$) in the inclusive production of identified hadrons, $vec{e}~$+$~^3text{He}^{uparrow}rightarrow h+X$, using a longitudinally polarized 5.9 GeV electron beam and a transversely polarized $^3rm{He}$ target. Hadrons ($pi^{pm}$, $K^{pm}$ and proton) were detected at 16$^{circ}$ with an average momentum $<$$P_h$$>$=2.35 GeV/c and a transverse momentum ($p_{T}$) coverage from 0.60 to 0.68 GeV/c. Asymmetries from the $^3text{He}$ target were observed to be non-zero for $pi^{pm}$ production when the target was polarized transversely in the horizontal plane. The $pi^{+}$ and $pi^{-}$ asymmetries have opposite signs, analogous to the behavior of $A_text{LT}$ in semi-inclusive deep-inelastic scattering.
We report the first measurement of the double-spin asymmetry $A_{LT}$ for charged pion electroproduction in semi obreakdash-inclusive deep obreakdash-inelastic electron scattering on a transversely polarized $^{3}$He target. The kinematics focused on the valence quark region, $0.16<x<0.35$ with $1.4<Q^{2}<2.7,textrm{GeV}^{2}$. The corresponding neutron $A_{LT}$ asymmetries were extracted from the measured $^{3}$He asymmetries and proton over $^{3}$He 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 $^{3}$He and the neutron, while our $pi^{+}$ asymmetries are consistent with zero.
The target and double spin asymmetries of the exclusive pseudoscalar channel $vec evec pto eppi^0$ were measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of $Q^2$, $x_B$, $-t$ and $phi$. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of generalized parton distributions (GPDs) provides the first insight on the chiral-odd GPDs $tilde{H}_T$ and $E_T$, and complement previous measurements of unpolarized structure functions sensitive to the GPDs $H_T$ and $bar E_T$. These data provide necessary constraints for chiral-odd GPD parametrizations and will strongly influence existing theoretical handbag models.
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