排序方式: 共有19条查询结果,搜索用时 15 毫秒
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Brodowski W Bilger R Calén H Clement H Ekström C Fransson K Greiff J Häggström S Höistad B Johanson J Johansson A Johansson T Kilian K Kullander S Kupść A Marciniewski P Morosov B Oelert W Pätzold J Ruber RJ Schepkin M Scobel W Seluzhenkov I Stepaniak J Sukhanov A Turowiecki A Wagner GJ Wilhelmi Z Zabierowski J Zlomanczuk J 《Physical review letters》2002,88(19):192301
The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found. 相似文献
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I. Gnesi N. Angelov M. Artoni S. Baginyan F. Balestra Yu. Batusov P. Batyuk I. Belolaptikov A. Bianconi T. Blokhintseva M. Chiosso M. L. Colantoni M. Corradini A. Dem’yanov V. Drozdov V. Frolov R. Garfagnini A. Grasso V. Grebenyuk V. Ivanov A. Kirilov V. Kovalenko E. Lodi Rizzini V. Lyashenko A. Maggiora A. Moiseenko V. Panyushkin D. Panzieri B. Parsamyan G. Piragino G. Pontecorvo A. Rozhdestvensky N. Russakovich E. Scalas M. Schepkin F. Tosello L. Venturelli G. F. Zosi 《The European Physical Journal A - Hadrons and Nuclei》2011,47(1):1-10
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Cross sections for processes involving three or more identical nucleons in the final state are expected to be strongly suppressed near the threshold because of the Pauli exclusion principle. It is shown that the Migdal-Watson effect (final-state interaction between nucleons) removes this suppression. 相似文献
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Victor D. Schepkin William W. Brey Peter L. Gor'kov Samuel C. Grant 《Magnetic resonance imaging》2010
The first in vivo sodium and proton magnetic resonance (MR) images and localized spectra of rodents were attained using the wide bore (105 mm) high resolution 21.1-T magnet, built and operated at the National High Magnetic Field Laboratory (Tallahassee, FL, USA). Head images of normal mice (C57BL/6J) and Fisher rats (∼250 g) were acquired with custom designed radiofrequency probes at frequencies of 237/900 MHz for sodium and proton, respectively. Sodium MR imaging resolutions of ∼0.125 μl for mouse and rat heads were achieved by using a 3D back-projection pulse sequence. A gain in SNR of ∼3 for sodium and ∼2 times for proton were found relative to corresponding MR images acquired at 9.4 T. 3D Fast Low Angle Shot (FLASH) proton mouse images (50×50×50 μm3) were acquired in 90 min and corresponding rat images (100×100×100 μm3) within a total time of 120 min. Both in vivo large rodent MR imaging and localized spectroscopy at the extremely high field of 21.1 T are feasible and demonstrate improved resolution and sensitivity valuable for structural and functional brain analysis. 相似文献
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J. Gr?ter P.A. Amaudruz R. Bilger P. Camerini J. Clark H. Clement E. Friedman L. Felawka S.N. Filippov E. Friagiacomo Y.K. Gavrilov E. Gibson N. Grion G.J. Hofman B. Jamieson T.L. Karavicheva M. KermaniPresent address: Sonigistix Corporation Richmond B.C. Canada VA-E--> E.L. Mathie R. Meier G. Moloney D. Ottewell J. P?tzold O. Patarakin K. Raywood R. Rui M. Schepkin M.E. Sevior G.R. Smith H. Staudenmaier R. Tacik G. Tagliente G.J. Wagner M. Yeomans 《The European Physical Journal A - Hadrons and Nuclei》1999,4(1):5-7
A search for the production of a bound trineutron state has been performed using the reaction 3He(π−,π+)nnn at incident pion energies of 65, 75, and 120 MeV. No evidence for the existence of the 3n was found, and an upper limit for the production cross section of approximately 30 nb/sr (2σ confidence level) was obtained.
Received: 22 October 1998 相似文献
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U. Siodlaczek P. Achenbach J. Ahrens J.R.M. Annand H.-J. Arends R. Beck R. Bilger H. Clement V. Hejny M. Kotulla B. Krusche V. Kuhr R. Leukel J.C. McGeorge V. Metag R. Novotny V. Olmos de León F. Rambo M. Schepkin A. Schmidt I. Seluzhenkov H. Ströher G.J. Wagner Th. Walcher J. Weiß F. Wissmann M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):365-371
Differential cross-sections for the reactions d (γ,π0)d and d (γ,π0)pn have been measured at MAMI with the TAPS detector setup in the energy range 140 MeV < E
γ < 306 MeV. By use of the Glasgow tagging spectrometer an 0.8 MeV energy resolution for photons incident on the target was
achieved. The π0 missing energy resolution was sufficient for a reliable separation of coherent and incoherent channels. The data for the
break-up channel exhibit very strong final state interaction effects, whereas the observed angular dependence of the inclusive
process d (γ,π0)X is in quantitative agreement with predictions for a quasi-free process. The observed absolute d (γ,π0)X cross-sections, on the other hand, are significantly smaller than predicted by the quasi-free process for E
γ >∼ 250 MeV. Associating this failure with the π0 photoproduction on the neutron would suggest that its cross-section is up to 25% below the presently believed value.
Received: 13 February 2001 / Accepted: 13 April 2001 相似文献
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Yu. A. Batusov T. D. Blokhintseva G. B. Pontecorvo F. Balestra M. P. Bussa G. Piragino M. G. Schepkin 《The European Physical Journal A - Hadrons and Nuclei》2006,28(1):11-17
The invariant-mass spectra of the ppπ- and pp systems produced in the double charge exchange (DCX) of positively charged pions on photoemulsion are analysed. A pronounced
peak is observed in the ppπ- invariant-mass spectrum, while the Mpp spectrum exhibits a strong Migdal-Watson effect of the proton-proton final-state interaction. These findings are in favor
of the NN-decoupled NNπ pseudoscalar resonance with T = 0 called d'. 相似文献