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  • 13.75.Cs  (49)
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  • 1
    ISSN: 1434-601X
    Keywords: 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We re-analyze the spectator proton distribution for ¯pd→π + π− π− p. For this channel previous calculations underestimated the cross section for proton momenta of 300 to 600 MeV/c by about a factor 7 while the channels with higher pion multiplicities and the ¯pd→K¯ Kmπp reactions were well explained. By using detailed experimental information on ¯pn and ¯pp annihilation, meson rescattering can in fact explain the cross section also for the 3π case. The¯ pp annihilation followed by charge exchange pion rescattering is much larger than in the 5π case. Vector meson exchange is small but not negligible at high spectator momenta.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 326 (1987), S. 131-138 
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 12.40.Qq ; 25.40.-h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Elastic scattering of 180 MeV antiprotons by several closed-shell nuclei are analyzed using Glauber's multiple scattering theory. Spin observables in elastic scattering are obtained within this framework. The sensitivity of the polarizations to the spin-flip amplitudes are discussed in terms of the¯NN potential models used for the calculations. Spineffects in angular distribution are found to be small.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 326 (1987), S. 191-193 
    ISSN: 1434-601X
    Keywords: 25.40.Ve ; 13.75.Cs ; 21.30.+ y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The elementary reaction pp→nΔ + +, through which the6Li(p, Δ + +)6He reaction proceeds, is considered as the flip of spins and isospins of two quarks, one in each of the two quark bags of the interacting nucleons. Using the experimental data on the6Li(p, Δ + +)6He reaction at 1.04 GeV and the distorted wave Born approximation (DWBA) for the reaction mechanism, the strength of the spin-isospin quark-quark interaction is determined. It is found to be 70 MeV fm3.
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  • 4
    ISSN: 1434-601X
    Keywords: 12.35.Ht ; 13.75.Cs ; 21.10.Ky
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A detailed analysis is made of the pair,ρπγ-currents, retardation effects and six-quark admixtures to the charge, quadrupole form factors and to the deuteron polarization. It is shown that the elasticeD-scattering cross section allowing for the meson exchange currents can be described by introducing a six-quark admixture with probability 3.5%. It is predicted that the behaviour of the deuteron polarization tensor at q〉4 fm−1 essentially depends on 6q-admixture.
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  • 5
    ISSN: 1434-601X
    Keywords: 36.10.Gv ; 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The strong ¯p-nucleus spin-orbit interaction was investigated in a measurement of the strong-interaction effects of the 9→8 transition in ¯p 174Yb at the Low-Energy Antiproton Ring (LEAR) at CERN. This measurement was part of an experimental programme where, for the first time, the fine-structure components of the last observable X-ray transition in a ¯p atom, which carries information on the strong ¯p-nucleus interaction, were resolved and studied individually. The observed splitting ΔE exp=2408±26 eV consists of the electromagnetic fine-structure splitting ΔE FS=2350 eV and an additional splitting Δɛ=58±26 eV. In addition, one finds a significant difference in the level widths of Δ=195±59 eV with the larger value⇊=1216±41 eV for the lower fine-structure level. This experiment follows an earlier measurement on ¯p 138Ba, where the transition 8→7 is influenced by the strong interaction. In this case, however, the fine-structure components could not be resolved. The results for174Yb may be attributed to a spin-orbit (LS) term in the complex strong-interaction potential.
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  • 6
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 12.40.Qq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The on-shell equivalence of the deep quantum-chromodynamically motivated realistic nucleon-nucleon interaction recently proposed by Kukulin et al. with more conventional repulsive-core forces is investigated by eliminating its unphysical deeply bound states, while preserving its scattering properties and the binding energy of the deuteron. The resulting interaction, which is built both in the singlet and triplet channels, displays ar −2 singular repulsive core followed by a shallow attraction of intermediate range, in good semiquantitative agreement with existing realistic nucleon-nucleon interactions.
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  • 7
    ISSN: 1434-601X
    Keywords: 12.35.Ht ; 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The importance of approximate isospin selection rules observed inN¯ N annihilation at rest into two strange mesons is emphasized. The selection rules are traced back to a symmetry between amplitudes describing annihilation by the flux of quarks. Presumably the symmetry reflects the symmetry of ¯qq annihilation vertices. The relation of the symmetry to a quark — diquark substructure of the nucleon is discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 334 (1989), S. 329-341 
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 24.10.Ht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the wave-functions, energy shifts and widths of low lying protonium states using different optical potentials (Dover-Richard, Kohno-Weise). The importance of tensor and isospin coupling is studied and the initial state distortion is compared for protonium annihilation andp¯p annihilation in flight at low energy. We study the range of distances at which annihilation actually occurs in protonium. We also analyse the effect of the initial state interaction on two meson branching ratios and underline that it may dramatically change the predictions of those microscopic models which are based only on phase space and simple quark diagrams.
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  • 9
    ISSN: 1434-601X
    Keywords: 13.75.Cs ; 21.30.+y ; 11.30.Hv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Validity and consequences of the quark line rule (QLR) in nucleon (N)— antinucleon (¯N) annihilations into two or three mesons at LEAR energies are investigated. Recent data on proton-antiproton annihilation into anη orη′ together with additional non-strange pseudoscalar or vector meson (s) is used to successfully test the rule. We find that for present data any pseudoscalar meson mixing angle ΦPS restricted to −260〈ΦPS〈−2.20 is approximately consistent with the QLR. Since the assumptions leading to this test are valid in any present-day quark model of nucleon-antinucleon annihilation, improvement of the data will be of utmost importance. If proven valid, the QLR can be used to test if quark-antiquark annihilation dominates over quark exchange inN¯N → mesons at LEAR energies or vice versa. Previously proposed tests of the quark line diagrams (annihilation or rearrangement) describing the quark flavor flux under either of these assumptions are worked out. We investigate without a definite conclusion if dominance of annihilation over rearrangement is consistent with present data onp¯p → π0 π0,ηη, π0ρ0, π0ω, ηρ0,ηω, ρ0ρ0,ωω. As a main consequence, dominance of annihilation predicts without any ambiguity equality of the proton-antiproton annihilation cross sections σ(ωω) and σ(ρ0ρ0). Further consequences of dominance of either annihilation or rearrangement diagrams for proton-antiproton annihilation into two or three mesons are also worked out. We compare the predictions of the models we discuss to the sparse present data. It is emphasized that our predictions only exploit the quark flavor flux within the quark line diagrams that are assumed to dominate. They thus are independent of gluon contributions to these diagrams.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 335 (1990), S. 355-359 
    ISSN: 1434-601X
    Keywords: 32.00 ; 36.00 ; 13.75.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent measurements of fine-structure splitting in $$\bar p$$ atoms of174Yb are analysed. Effects of nuclear deformation are calculated. The strength of nuclear spin-orbit coupling is determined and its implications on theN $$\bar N$$ potential are discussed.
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