29 research outputs found

    π+\pi^+ photoproduction on the proton for photon energies from 0.725 to 2.875 GeV

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    Differential cross sections for the reaction Îłp→nπ+\gamma p \to n \pi^+ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.725 to 2.875 GeV. Where available, the results obtained here compare well with previously published results for the reaction. Agreement with the SAID and MAID analyses is found below 1 GeV. The present set of cross sections has been incorporated into the SAID database, and exploratory fits have been made up to 2.7 GeV. Resonance couplings have been extracted and compared to previous determinations. With the addition of these cross sections to the world data set, significant changes have occurred in the high-energy behavior of the SAID cross-section predictions and amplitudes.Comment: 18 pages, 10 figure

    Photodisintegration of 4^4He into p+t

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    The two-body photodisintegration of 4^4He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid 4^4He target. This is the first measurement of the photodisintegration of 4^4He above 0.4 GeV. The differential cross sections for the γ\gamma4^4He→pt\to pt reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of 3^3He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV .Comment: 13 pages submitted in one tgz file containing 2 tex file and 22 postscrip figure

    Exclusive Photoproduction of the Cascade (Xi) Hyperons

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    We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.Comment: submitted to Phys. Rev.

    First measurement of target and double spin asymmetries for polarized e- polarized p --> e p pi0 in the nucleon resonance region above the Delta(1232)

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    The exclusive channel polarized proton(polarized e,e prime p)pi0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the pi0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A_{1/2} and S_{1/2} for the Roper resonance N(1400)P11, and the N(1535)S11 and N(1520)D13 states.Comment: 13 pages, 13 figure

    Editorial

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    Editorial

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    Energy from nuclear fission: an introduction

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    This book provides an overview on nuclear physics and energy production from nuclear fission. It serves as a readable and reliable source of information for anyone who wants to have a well-balanced opinion about exploitation of nuclear fission in power plants. The text is divided into two parts; the first covers the basics of nuclear forces and properties of nuclei, nuclear collisions, nuclear stability, radioactivity, and provides a detailed discussion of nuclear fission and relevant topics in its application to energy production. The second part covers the basic technical aspects of nuclear fission reactors, nuclear fuel cycle and resources, safety, safeguards, and radioactive waste management. The book also contains a discussion of the biological effects of nuclear radiation and of radiation protection, and a summary of the ten most relevant nuclear accidents. The book is suitable for undergraduates in physics, nuclear engineering and other science subjects. However, the mathematics is kept at a level that can be easily followed by wider circles of readers. The addition of solved problems, strategically placed throughout the text, and the collections of problems at the end of the chapters allow readers to appreciate the quantitative aspects of various phenomena and processes. Many illustrations and graphs effectively supplement the text and help visualising specific points
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