Hidden Strangeness in the Proton? Determination of the Real Part of the Isospin Even - Forward Scattering Amplitude of Pion Nucleon Scattering at 54.3-{MeV}

Wiedner, U. ; Goring, K. ; Jaki, J. ; et al.
Phys.Rev.D 40 (1989) 3568-3581, 1989.
Inspire Record 287810 DOI 10.17182/hepdata.23079

The contradiction of the σ term of pion-nucleon scattering as deduced from the Karlsruhe-Helsinki phase shifts with the smaller value calculated by the chiral perturbation theory of QCD is well known. In an effort to clarify the discrepancy we have determined the real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering at a pion energy Tπ=54.3 MeV by measurement of the elastic scattering of positive and negative pions on protons in the Coulomb-nuclear interference region. The deduced value is in agreement with the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. The resulting large value of the σ term may be interpreted as being due to the influence of s¯s sea pairs even at large distances (small Q2) as previously suggested by the European Muon Collaboration measurement of deep-inelastic scattering of polarized muons on polarized protons.

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DCS for π − p elastic scattering from 1.2 to 3.0 GeV/ c and phase shift analysis

Aplin, P.S. ; Cowan, I.M. ; Gibson, W.M. ; et al.
Nucl.Phys.B 32 (1971) 253-284, 1971.
Inspire Record 1104030 DOI 10.17182/hepdata.69638

Differential cross sections have been measured for π − p elastic scattering at laboratory momenta in the range 1.2 to 3.0 GeV/ c for the c.m. range 0.97 > cos θ ∗ > −0.98 . The corresponding mass range is 1.78 to 2.56 GeV/ c 2 . The data was obtained from a counter experiment in which the scattered pions and protons were detected in coincidence by arrays of scintillation counters.

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Differential Cross-Sections for K- p Elastic Scattering from 1.4-GeV/c to 1.9-GeV/c

Abe, K. ; Barnett, B.A. ; Goldman, J.H. ; et al.
Phys.Rev.D 12 (1975) 6-14, 1975.
Inspire Record 103522 DOI 10.17182/hepdata.24826

We report here the results from an experiment to obtain differential cross sections for K−p elastic scattering in the laboratory momentum region from 1.4 to 1.9 GeV/c. These data span the region of a bump in the K−p total cross section at an energy of 2.05 GeV. Approximately 20000 elastic events were obtained at each of four momenta with an angular coverage of 0.9≥cosθc.m.≥−0.9. The data are intended to aid in phase-shift analyses of the resonances causing the bump in the total cross section and to study dip structures at constant values of the Mandelstam variables t and u.

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LEGENDRE POLYNOMIAL COEFFICIENTS.

FROM INTEGRATING LEGENDRE POLYNOMIAL FIT TO D(SIG)/DOMEGA. QUOTED ERRORS INCLUDE NORMALIZATION AND FITTING UNCERTAINTIES.