Session H10: Few-nucleon Systems

Beam-Target Double Spin Asymmetry in $\vec{D}(\vec{e},e'p)n$

Using the CLAS detector at Jefferson Lab, double spin asymmetries ($A_{||}$) for quasi-elastic electron scattering off the deuteron have been measured at several beam energies. The data were collected during the EG1 experiment, which scattered longitudinally polarized electrons from 1.6 to 5.8 GeV off a longitudinally polarized cryogenic ND$_{3}$ target. The double spin asymmetries were measured as a function of photon virtuality $Q^{2}$ (0.13-3.17 GeV), missing momentum (0.0-0.5 GeV), and the angle between the (inferred) ``spectator'' neutron and the momentum transfer direction ($\theta_{nq}$). The results from EG1b were compared with a recent model that includes final state interactions using a complete parameterization of nucleon-nucleon scattering. We will discuss our results for the double spin asymmetry and compare them to this model as well as a simplified model using the plane wave impulse approximation.   

Determination of the Azimuthal Asymmetry for Deuteron Photodisintegration at $E_\gamma=1.1-2.3$~GeV

Deuteron photodisintegration is a benchmark process for investigating the role of quarks and gluons in nuclei. Existing theoretical models of this process describe the cross sections with the same degree of success. Therefore, to distinguish between models, spin-dependent observables are crucial for a better understanding of the underlying dynamics. The induced polarization ($P_y$) and the polarization transfers ($C_{x'}$ and $C_{z'}$) have been instrumental in proving that a pQCD treatment is not applicable at medium energies; however, these observables are relatively insensitive to different non-perturbative models and do not provide further insight into the physics of the process. By contrast, the azimuthal asymmetry $\Sigma$ is predicted to have a large sensitivity and can help in identifying the energy at which the transition from the hadronic to the quark-gluon picture takes place. We present results for the azimuthal asymmetry for deuteron photodisintegration at photon energies $E_\gamma=$ 1.1-2.3~GeV and proton center-of-mass angles $\theta_p=$ 20$^\circ$-160$^\circ$ taken with the CLAS detector at Jefferson Lab. Our preliminary analysis shows that our results have the kinematic coverage and statistics needed to test the available non-perturbative QCD-inspired models.   

Isobar configurations in the $^3$He ground state

The probabilities of short-range correlations (SRC), meson-exchange currents and final-state interactions in nuclei contribute to the measured observables that are mostly being interpreted within strongly model-dependent pictures. Studying the short-distance structure and virtual nucleon excitations, especially isobar configurations in the nuclear ground state, are important subjects in experimental nuclear physics. Since the SRC are local high-density regions, it is likely that the quark distributions of nucleons would make a transition to non-nucleonic configurations. A number of theoretical calculations predict the probability of finding one or more nucleons in an excited state. In some studies, isobar excitations have been explicitly included in the few-body models. In this work we have explored a recent data set of photon-induced reactions from nuclear targets to study various photoproduction channels that contain one or more $\Delta$-isobar configurations, for example, the $\gamma$$^3$He $\rightarrow \Delta^{++}nn$ or $\gamma$$^3$He $\rightarrow \Delta^{++} \Delta^0 n$ reactions. Data were taken with CLAS in Hall B at Jefferson Laboratory using an incident photon-beam energy of 0.5-1.5 GeV on a $^3$He target. Preliminary results and future plans will be discussed.   

Three-body photodisintegration of 3He with double polarizations at incident photon energies E 12.8 MeV and 14.7 MeV

We report on the study of three-body photo-disintegration of polarized $^3$He using a circularly polarized $\gamma$ beam at incident photon energies 12.8 MeV and 14.7 MeV. The experiment was carried out at the High Intensity $\gamma$ Source (HI$\gamma$S) facility located at Triangle Universities Nuclear Laboratory. A high-pressure $^3$He cell was employed as target and it was polarized using the spin exchange optical pumping (SEOP) technique of hybrid alkali. The neutrons from the three-body photo-disintegration were detected using 16 liquid scintillator fast neutron detectors positioned in the reaction plane at 8 angles varying from 30$^\circ$ to 165$^\circ$. Preliminary results on asymmetry and spin-dependent differential cross sections for both energies will be presented and compared with the three-body calculations using both CD Bonn and AV18 potentials.   

A$_y$ Measurement from $^3\mbox{He}^\uparrow(e,e'n)$ Scattering at Jefferson Lab

Recently A$_y$ asymmetry measurements have been conducted in Jefferson Lab's Hall A through electron scattering from a vertically polarized $^3$He target. Experiment E08-005 measured the target single-spin asymmetry A$_y$ in the quasi-elastic $^3\mbox{He}^\uparrow(e,e'n)$ reaction. Plane wave impulse approximation (PWIA) predicts that A$_y$ should be exactly zero. A previous experiment at Q$^2$ of 0.2 (GeV/c)$^2$, where full calculations of Laget and Nagorny indicated A$_y$ to be small, showed a large asymmetry as calculated by the Bochum group using Faddeev calculations to solve the three-body problem exactly. The recent experiment measured this asymmetry at Q$^2$ of 0.1 (GeV/c)$^2$, 0.5 (GeV/c)$^2$ and 1.0 (GeV/c)$^2$. This is the first measurement of A$_y$ at large Q$^2$, which is another region where A$_y$ is expected to be small. Any non-zero result is an indication of effects beyond simple impulse approximation. This measurement will test the models used to extract neutron form factors from polarized $^3$He. Details of the measurement will be presented.   

Cluster calculations for the $^6$He and $^9$Be spectra

The $^6$He and $^9$Be nuclei are considered as a mirror cluster systems $\alpha nn$ and $\alpha \alpha n$. The excitation energies of the low-lying levels for $^6$He and $^9$Be nuclei are evaluated. These cluster calculations are based on the configuration-space Faddeev equations. The method of analytical continuation in a coupling constant is used to calculate resonance parameters [1]. Our goal is to show possibility for a reliable description of the $^6$He and $^9$Be within the cluster model using pair local potentials. We focus on the new $\alpha n$ interaction model proposed in [1]. We assume that both, central $p$-wave component and spin-orbital component of $\alpha n$ potential mainly determine the excitation spectra structure of these nuclei. The low-lying spectrum of $^9$Be is well reproduced with this potential. The results for excitation resonance energies of the $\alpha nn$(0+,2+,1+) systems are presented and compared with the experimental data (http://www.tunl.duke.edu/nucldata/chain/06.shtml) and those from other calculations [2]. \\[4pt] [1] I. Filikhin, V.M. Suslov and B. Vlahovic, Few-Body Systems 50, 255 (2011). \\[0pt] [2] S.N. Ershov, T. Rogde, B.V. Danilin, J.S. Vaagen, I.J. Thompson, F.A. Gareev, Phys. Rev. C 56, 1483 (1997).   

Dynamics of dud, dut in superstrong laser fields for laser induced nuclear fusion

Nuclear fusion occurs during the collision of selected isotopes of hydrogen with relative energy in the MeV(10**6 eV) regime. Such high energy ions can be generated by high power lasers applied to clusters [1] via the accumulated ponderomotive energies. However in such schemes laser induced collisions are random whereas as shown previously ultrashort superintense laser pulses can be used to control collisions in muonic molecules [2]. We present full 3-D dynamics from accurate Time-dependent Schroedinger equations, TDSE, s, of the isotopomers, pud, dud, dut in super intense laser pulses with intensities I~ 10**23 W/cm**2 to illustrate the possibility of inducing always head-on(zero-impact) collisions leading in principle to laser induced nuclear fusion, LINF. Due to its heavy mass(mu/me=185.8) the muonic molecular ions are stable to ionization up to intensities I=10**23 W/cm**2 and recollision of the heavy particles (p,td,t) will be shown to be controllable by few cycle superintense laser pulses leading to LINF.The nonsymmetric isotopomers dut and put manifest enhanced fusion due to the presence of permanent dipole moments.\\[4pt] [1] KWD Ledingham et al, Science 300, 1107 (2003)\\[0pt] [2] S Chelkowski, PB Corkum, AD Bandrauk, Phys Rev Lett 93, 083602(2004)   

Observation of Electron Cloud Stabilized 1 MeV Beam-Beam d+d Reactons in Self-Colliding Orbits and Feasibility of Electric Isotope Breeder

D-D Self-Collider $^{1,2}$ is only system in which beam-beam nuclear reactions demonstrated MeV energies. 1.45 MeV DC beam of D$_{2}^{+}$ was injected into center of a weak-focusing magnetic field (Ni Ti) B=3.12 Tesla, and dissociated into 2 d$^{+}$ stored in Self-Colliding Orbits$^{3}$. Energy confinement time T = 23 s (vacuum limited p=10$^{-9}$ torr), stabilized by driven electron oscillations$^{4}$. A simulation$^{5}$ shows that 1 DD neutron is produced at an energy cost of 5.36 MeV/n i.e. 140 MWh/g= {\$}8,360/g vs. {\$}160,000/g from beam - target. Simultaneously produced He$^{3}$ and T are not only free, but bring 45 fold gain. 5 d's of 0.75 MeV generate 1He$^{3}$ +1T +1p+ 1n at cost 5.36 MeV. Hence, it will produce 2 He$^{3}$ nuclei (1 He-3, 1 T) plus energy gain of 161 MeV. This will be reduced by the energy gain thus reducing cost to 4.5 from 5.6 MeV. Assumed ion density 5x10 $^{14}$ was achieved in plasmas. Beam injection 100 mA. 1. PRL 54, 796 (1985) NIM A 271 p,.1-167; 2. AIP CP 311, 292 (93); 3. PRL 70, 1818 (93); 4.Part. Acc.1, (70); 5. ``50 Years with Fission'' Symp.Nat. Ac Sci., p. 761 (89)