235 research outputs found

    Performance of the neutron polarimeter NPOL3 for high resolution measurements

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    We describe the neutron polarimeter NPOL3 for the measurement of polarization transfer observables DijD_{ij} with a typical high resolution of \sim300 keV at TnT_n \simeq 200 MeV. The NPOL3 system consists of three planes of neutron detectors. The first two planes for neutron polarization analysis are made of 20 sets of one-dimensional position-sensitive plastic scintillation counters with a size of 100 cm ×\times 10 cm ×\times 5 cm, and they cover the area of 100 ×\times 100 cm2\mathrm{cm}^2. The last plane for detecting doubly scattered neutrons or recoiled protons is made of the two-dimensional position-sensitive liquid scintillation counter with a size of 100 cm ×\times 100 cm ×\times 10 cm. The effective analyzing powers Ay;effA_{y;\mathrm{eff}} and double scattering efficiencies ϵD.S.\epsilon_{\mathrm{D.S.}} were measured by using the three kinds of polarized neutrons from the 2H(p,n)pp{}^{2}{\rm H}(\vec{p},\vec{n})pp, 6Li(p,n)6Be(g.s.){}^{6}{\rm Li}(\vec{p},\vec{n}){}^{6}{\rm Be}(\mathrm{g.s.}), and 12C(p,n)12N(g.s.){}^{12}{\rm C}(\vec{p},\vec{n}){}^{12}{\rm N}(\mathrm{g.s.}) reactions at TpT_p = 198 MeV. The performance of NPOL3 defined as ϵD.S.(Ay;eff)2\epsilon_{\mathrm{D.S.}}(A_{y;\mathrm{eff}})^2 are similar to that of the Indiana Neutron POLarimeter (INPOL) by taking into account for the counter configuration difference between these two neutron polarimeters.Comment: 28 pages, 18 figures, submitted to Nucl. Instrum. Methods Phys. Res.

    Two-pion-exchange contributions to the pp\to pp\pi^0 reaction

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    Our previous study of the near-threshold pp\to pp\pi^0 reaction based on a hybrid nuclear effective field theory is further elaborated by examining the momentum dependence of the relevant transition operators. We show that the two-pion exchange diagrams give much larger contributions than the one-pion exchange diagram, even though the former is of higher order in the Weinberg counting scheme. The relation between our results and an alternative counting scheme, the momentum counting scheme, is also discussed.Comment: 11 pages, minor change, a few references are adde
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