5,366 research outputs found

    Nuclear effects in positive pion electroproduction on the deuteron near threshold

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    Positive pion electroproduction from the deuteron near threshold has been considered within an approach based on the unitary transformation method. The gauge independence of the treatment is provided by using an explicitly gauge independent expression for the reaction amplitude. The results of calculations for kinematics of the experiments on forward-angle π+\pi^+ meson electroproduction accomplished at Saclay and Jefferson Laboratory are discussed and compared with those given by the impulse approximation. It is shown that the observed behaviour of the cross sections is in accordance with the calculations based on the pion-nucleon dynamics. In particular, the pion production rate suppression in the 2H(e,eπ+)nn^2H(e,e'\pi^+)nn reaction compared to that for the 1H(e,eπ+)n^1H(e,e'\pi^+)n one can be due to such ``nuclear medium'' effects as nucleon motion and binding along with Pauli blocking in the final nnnn state.Comment: 15 pages, 8 figure

    Polarized Proton Pionic Capture in Deuterium as a Probe of 3N Dynamics

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    The proton analyzing power Ay in pion production reaction pd --> pi0 3He has been calculated including one- and two-body meson production mechanisms with a proper treatment of the three-nucleon dynamics and an accurate solution of the 3N bound-state problem for phenomenological two-nucleon potentials. In the region around the Delta resonance, the structure of the analyzing power can be understood once interference effects among amplitudes describing intermediate Delta N formation in different orbital states are considered along with the additional interference with the S-wave pion production amplitudes. Then, the inclusion of three-nucleon dynamics in the initial state produces the structure of the analyzing power that has been observed experimentally.Comment: 9 pages, 5 figure

    Magnetic polarizability of hadrons from lattice QCD

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    We extract the magnetic polarizability from the quadratic response of a hadron's mass shift in progressively small static magnetic fields. The calculation is done on a 24x12x12x24 lattice at a = 0.17 fm with an improved gauge action and the clover quark action. The results are compared to those from experiments and models where available.Comment: 3 pages, 3 figures, contribution to Lattice 2002 (spectrum

    Comment on ``Evidence for Narrow Baryon Resonances in Inelastic pp Scattering''

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    Compton scattering data are sensitive to the existence of low-mass resonances reported by Tatischeff et al. We show that such states, with their reported properties, are excluded by previous Compton scattering experiments.Comment: One page, submitted to PR

    Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

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    Differential cross sections for Compton scattering from the deuteron were measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at nominal laboratory angles of 4545^\circ, 125125^\circ, and 135135^\circ. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and difference of the isospin-averaged nucleon polarizabilities, αN+βN=17.4±3.7\alpha_N + \beta_N = 17.4 \pm 3.7 and αNβN=6.4±2.4\alpha_N - \beta_N = 6.4 \pm 2.4 (in units of 10410^{-4} fm3^3), have been determined. By combining the latter with the global-averaged value for αpβp\alpha_p - \beta_p and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of αn=8.8±2.4\alpha_n= 8.8 \pm 2.4(total) ±3.0\pm 3.0(model) and βn=6.52.4\beta_n = 6.5 \mp 2.4(total) 3.0\mp 3.0(model), respectively.Comment: 4 pages, 2 figures, revtex. The text is substantially revised. The cross sections are slightly different due to improvements in the analysi

    Yield and content of biologically active substances in blue honeysuckle fruit (Lonicera caerulea L.) grown in the Forest Steppe of Ukraine

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    Received: July 28th, 2022 ; Accepted: September 26th, 2022 ; Published: October 20th, 2022 ; Correspondence: [email protected] blue honeysuckle (Lonicera caerulea L.) is a relatively new crop in Ukraine, its industrial cultivation is only 100 hectares. The main constraints are the lack of varieties with high yield and nutritional value of berries. Therefore, a study of the yield and quality of introduced varieties is necessary and relevant, both for producers and breeders. With our research, we determined the potential of the early stage of blue honeysuckle berries under the conditions of their cultivation in the Forest Steppe of Ukraine and the weather conditions of the year of the specified region. We assessed how early we can get a crop and set what quality and what it will be. To clearly understand the quality of the grown fruits, their average weight, size and uniformity were studied. From nutritional indicators of fruit quality, the content of dry matter, soluble solids, sugars and titrated acids was studied, from biologically active substances, the content of vitamin C and total phenolic was determined. It was found that in the zone of the Forest Steppe of Ukraine from the studied group of varieties, the highest yield potential, 3.13 kg from a bush for the second year of fruiting and fruit mass 2.4 g, had a variety of Canadian breeding ‘Boreal Beauty’. The fruits of the cultivars ‘Duet’ (4.3) and ‘Boreal Blizzard’ (4.5) were distinguished by the balance of taste according to the sugar-acid index, and the maximum amount of total phenolics for the studied group of varieties was accumulated by the fruits of ‘Boreal Beast’ (1,000 mg 100 g-1 )

    Congruence of Human Organizations and Missions: Theory versus Data

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    1999 Command and Control Research and Technology Symposium (CCRTS), June 29 - July 1, 1999, U.S. Naval War College, Rhode IslandIn this paper, we present a methodology for quantifying the degree of fit between a mission and an organization based on the closeness between the task structure (i.e., resource requirements and task interdependence) and the DM-asset allocation across the organization (i.e., amount and distribution of resource capabilities among DMs, and organizational processes). This closeness is based on three main characteristics of organizational performance: workload balance, communication requirements, and DM-DM dependence. These characteristics are affected, in turn, by the interactions and interdependencies of the organizational processes and the demands of the mission scenario. Invariably, coordination is essential to achieve good performance because the information required for decisionmaking is often distributed. However, excessive DM-DM communication and coordination are harmful to performance, since they increase the processing workload/overhead that delays task execution. Performance improvements can be obtained by changing the structure and processes of an organization to decrease the requisite coordination, while balancing the levels of workload across the organization and reducing inter DM dependence.This work was supported by the Office of Naval Research under contract # N00014-00-1-0101

    Neutron polarizabilities investigated by quasi-free Compton scattering from the deuteron

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    Measuring Compton scattered photons and recoil neutrons in coincidence, quasi-free Compton scattering by the neutron has been investigated at MAMI (Mainz) at thetaγlab=136otheta^{lab}_\gamma=136^o in an energy range from 200 to 400 MeV. From the data a polarizability difference of αnβn=9.8±3.6(stat)1.1+2.1(syst)±2.2(model)\alpha_n - \beta_n = 9.8 \pm 3.6(stat)^{+2.1}_{-1.1}(syst)\pm 2.2(model) in units of 104fm310^{-4}fm^3 has been determined. In combination with the polarizability sum αn+βn=15.2±0.5\alpha_n+\beta_n= 15.2\pm 0.5 deduced from photo absorption data, the neutron electric and magnetic polarizabilities, αn=12.5±1.8(stat)0.6+1.1(syst)±1.1(model)\alpha_n=12.5\pm 1.8(stat)^{+1.1}_{-0.6}(syst)\pm 1.1(model) and βn=2.71.8(stat)1.1+0.6(syst)1.1(model)\beta_n = 2.7\mp 1.8(stat)^{+0.6}_{-1.1}(syst)\mp 1.1(model), are obtained
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