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  • 11
    Electronic Resource
    Electronic Resource
    A new determination of the πN coupling constantf 2 (1969)
    Springer
    The European physical journal 229 (1969), S. 217-223 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coupling constantf 2 has been determined from forward dispersion relations for theπN helicity flip and no-flip amplitudes, using the recent information on total cross sections, phase shifts and charge exchange forward cross sections. The calculation gives also the values of the amplitudes and the first derivative at the crossing symmetry point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01396248
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  • 12
    Electronic Resource
    Electronic Resource
    On the rôle of ρ-exchange in low energy πN scattering (1968)
    Springer
    The European physical journal 214 (1968), S. 381-387 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is pointed out that important features of the low energyπN charge-exchange amplitude differ considerably from the prediction of theρ-dominance model. — Without further improvements the Cini-Fubini approximation does not lead to a reliable determination of theρ-coupling constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379980
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  • 13
    Electronic Resource
    Electronic Resource
    The πN partial waves at low energies and in the unphysical region (1969)
    Springer
    The European physical journal 221 (1969), S. 134-140 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The real parts of theπN partial wave amplitudesf l± (−) have been calculated from fixed-t dispersion relations, using phase shifts up to 2 GeV and the reggeizedp-exchange model at higher energies. The comparison with Ref l± (−) as calculated directly from phase shifts shows to what extent the input is consistent with the fixed-t relation. The result is also of interest for the test of simple models, in particular for the comparison with predictions from current algebra. — A new evaluation of the partial wave dispersion relation forf 0+ (−) is presented. Combined with the first method it shows that the determination of thep-coupling parameter is based on an assumption which is difficult to justify.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01392138
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  • 14
    Electronic Resource
    Electronic Resource
    The real part of the πN diffraction amplitude (1974)
    Springer
    The European physical journal 268 (1974), S. 75-84 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The real part of the invariant isospin evenπ N amplitudeC +≡A′ + at ¦t¦≲0.4 (GeV/c)2 is determined from the condition thatC + fulfills the fixed-t dispersion relation, is compatible with this amplitude as reconstructed from phase shifts up to 1.5 GeV/c and leads to differential cross sections above 3 GeV/c in agreement with the experimental data.-The result for ReC +/ImC + is remarkably large (−0.5 att=−0.3 (GeV/c)2 and 6 GeV/c) and up to 20 GeV/c its uncertainty is comparable with that in the upper part of the phase shift region.-Even at 40 GeV/c ReC + is far from being asymptotic because of large energy independent low energy contributions. The deviations from our simple high energy ansatz (k〉4GeV/c): ImC +(k, t)∼(k + m)exp(9t/2) are almost comparable with the experimental errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01670064
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  • 15
    Electronic Resource
    Electronic Resource
    Vergleich der Photoerzeugung von π0 am Proton mit der Voraussage nach der Dispersionstheorie (1960)
    Springer
    The European physical journal 159 (1960), S. 77-88 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The real parts of the photoamplitudesE 1S 1/2,M 1P 1/2,M 1P 3/2 have been calculated from the angular distribution of the reactionγ+p→p+π0 recently measured byGoldansky et al. at 160 to 240 MeV. One of the solutions fits pretty well to the theoretical prediction for theM 1P 3/2-amplitude according to the dispersion method ofChew, Goldberger, Low andNambu. There is a discrepancy forM 1P 1/2 ifα 11 is taken from the effective range formula, but the positive values ofα 11, necessary to give agreement, are not excluded by the results of the phase shift analysis, especially sincePontecorvo et al. have recently found positive values at higher energies. The prediction for the real part of theE 1 S1/2-amplitude agrees with the experimental data, if pretty large recoil corrections are added which had been neglected byChew et al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01338463
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  • 16
    Electronic Resource
    Electronic Resource
    Ward identities, dispersion relations and duality for πN scattering at low energies (1971)
    Springer
    The European physical journal 245 (1971), S. 387-410 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The full one-particle approximation to the Ward identities for πN scattering is investigated, taking into account elastic unitarity in thet-channel for πN- and ππ-amplitudes. The results for the one-particle contributions are compared with the corresponding expressions in the dispersion relation approach, wheret-channel exchanges are introduced into fixed-t dispersion relations by subtracting the lowest ππN¯N-partial wave amplitudes. Our method leads to a prescription for an isobaric model, in which double counting does not occur althoughs-,t- andu-channel exchanges are superimposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01395280
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  • 17
    Electronic Resource
    Electronic Resource
    Impact parameter expansion of πN scattering amplitudes at intermediate energies (1973)
    Springer
    The European physical journal 261 (1973), S. 371-400 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Impact parameter transforms of isospin even no-flip πN-amplitudes and of the overlap function are calculated from the new CERN phase shifts. The results are compared with different models.—The approximate equality of the partial wave and the impact transform forbq=(l+ 1/2) is valid for smalll and not for largel as frequently assumed. The “optical potential” has a repulsive core in the real part and rather flat tails beyond 0.5 fermi in the real and imaginary parts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01395696
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  • 18
    Electronic Resource
    Electronic Resource
    Discrepancies between πN charge exchange forward scattering data and the dispersion relation prediction (1970)
    Springer
    The European physical journal 240 (1970), S. 377-391 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The πN charge-exchange forward scattering amplitude has been recalculated, using the most recent total cross section data, charge independence and the forward dispersion relation. In general the prediction agrees rather well with the data, but there are several discrepancies which are considerably larger than the errors. Some of these discrepancies follow from the fact that a structure at small ¦t¦ has been ignored in the extrapolation. — The new fit gives an accurate value for the subtraction constant of the integral. It agrees with the evaluation of the unsubtracted integral at threshold, if, at high energies, the Regge behaviour for σ(π− p)—σ(π+ p) is inserted. This result favours the validity of Pomeranchuk's theorem. — An improved value forf 2 cannot be obtained at present because of the uncertainty following from charge-dependent effects at low energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01395574
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  • 19
    Electronic Resource
    Electronic Resource
    Zero trajectories of invariant πN amplitudes. I (1980)
    Springer
    The European physical journal 4 (1980), S. 333-344 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Zero trajectories of invariant πN amplitudes have been calculated from the results of the recent phase shift analyses of the Karlsruhe-Helsinki and CMU-LBL groups. It is remarkable that the zero patterns of all invariant amplitudesA, B (for elastic π± p scattering and also for the isospin even and odd combinations) are similar to each other. This is unexpected from dual models, in particular sinceB + contains the effects of diffraction. There are qualitative discrepancies with the zero pattern of Odorico's Linear Zero Model. The good agreement between the results derived from the two phase shift analyses indicates that the ambiguities have been resolved in the same way. The continuation of the trajectories to unphysical regions and several applications will be treated in the second part of this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01421575
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  • 20
    Electronic Resource
    Electronic Resource
    πN charge-exchange forward scattering at high energies (1973)
    Springer
    The European physical journal 261 (1973), S. 401-412 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The unsubtracted dispersion relation is not compatible with the charge-exchange data, if a power law is assumed for the total cross section difference at high energies and the exponent is taken from the fit to the Serpuchov data. However, there is no difficulty for the subtracted dispersion relation. Recent estimates of a finite high energy limit of the total cross section difference and a possible substantial curvature of thep-trajectory neart=0 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01395697
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