Triton photodisintegration in three-dimensional approach

Two- and three- particles photodisintegration of the triton is investigated in a three-dimensional (3D) Faddeev approach. For this purpose the Jacobi momentum vectors for three particles system and spin-isospin quantum numbers of the individual nucleons are considered. Based on this picture the three-nucleon Faddeev integral equations with the two-nucleon interaction are formulated without employing the partial wave decomposition. The single nucleon current as well as $\pi-$ and $\rho-$ like exchange currents are used in an appropriate form to be employed in 3D approach. The exchange currents are derived from AV18 NN force. The two-body t-matrix, Deuteron and Triton wave functions are calculated in the 3D approach by using AV18 potential. Benchmarks are presented to compare the total cross section for the two- and three- particles photodisintegration in the range of $E_{\gamma}<30 MeV$. The 3D Faddeev approach shows promising results

Antimatter Regions in the Early Universe and Big Bang Nucleosynthesis

We have studied big bang nucleosynthesis in the presence of regions of antimatter. Depending on the distance scale of the antimatter region, and thus the epoch of their annihilation, the amount of antimatter in the early universe is constrained by the observed abundances. Small regions, which annihilate after weak freezeout but before nucleosynthesis, lead to a reduction in the 4He yield, because of neutron annihilation. Large regions, which annihilate after nucleosynthesis, lead to an increased 3He yield. Deuterium production is also affected but not as much. The three most important production mechanisms of 3He are 1) photodisintegration of 4He by the annihilation radiation, 2) pbar-4He annihilation, and 3) nbar-4He annihilation by "secondary" antineutrons produced in anti-4He annihilation. Although pbar-4He annihilation produces more 3He than the secondary nbar-4He annihilation, the products of the latter survive later annihilation much better, since they are distributed further away from the annihilation zone.Comment: 15 pages, 9 figures. Minor changes to match the PRD versio

Polarized angular distributions of parametric x radiation and vacuum-ultraviolet transition radiation from relativistic electrons

We present quantifiable images of the angular distribution (AO's) of parametric X radiation (PXR) and vacuum-ultraviolet transition radiation (vuv TR) from 230 MeV electrons interacting with a silicon crystal. Both AD's are highly polarized. The vuv TR and optical TR data provide measurements of the beam energy and effective divergence angle. Using these quantities and separately known values of the electronic susceptibility |Xo|, we show that the measured PXR AD is in good agreement with the predictions of single crystal theory. Our analysis suggests a method to measure |Xo| using PXR AD's.Ths work was sponsored in part by DOE SBIR Grant No. DE-FG03-91er80199; NCI SBIR Grant no. 1-R43-CA60207-01 and the Canadian Natural Science and Engineering Research Counci

Quasimonochromatic x-ray source using photoabsorption-edge transition radiation

By designing transition radiators to emit x-rays at the foil material's K-, L-, or M-shell photoabsorption edge, the x-ray spectrum is narrowed. The source is quasimonochromatic, directional, and intense and uses an electron beam whose energy is considerably lower than that needed for synchrotron sources. Depending on the selection of foil material, the radiation can be produced wherever there is a photoabsorption edge. In this paper we report the results of the measurement of the x-ray spectrum from a transition radiator composed of 10 foils of 2-um titanium and exposed to low-current, 90.2-MeV electrons, The measured band of emission was from 3.2 5o 5 keV. In addition, a measurement was performed of the total power from a transition radiator composed of 18 foils of 2.o-um copper exposed to a high-average-current electron beam of 40 uA and at energies of 135, 172, and 200 MeV. The maximum measured power was 4.0 mW. The calculated band of emission was from 4 to 9 keV.National Science Foundation of the Small Business Innovative Research (SBIR) program, Grant no. PHY-8460914; Department of Energy SBIR program, Grant No. DE-FG03-90ER80872; Canadian Natural Science and Engineering Research Council and the Naval Postgraduate SchoolThis investigation was supported by a Special Research Opportunity Grant from the U.S. Office of Naval Research, Department of the Navy and by the Foundation Research Program of the Naval Postgraduate School (Monterey, Ca.)Approved for public release; distribution is unlimited