Low-energy differential cross sections of pion-proton ([pi][sup [plus minus]][ital p]) scattering. I. The isospin-even forward scattering amplitude at [ital T][sub [pi]]=32. 2 and 44. 6 MeV

Journal Article · Sat Apr 01 00:00:00 EST 1995 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.51.2144· OSTI ID:6546930

Joram, C; Metzler, M; Jaki, J; Kluge, W; Matthaey, H; Wieser, R ^[1]; Barnett, B M; Clement, H; Krell, S; Wagner, G J ^[2]

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1. Institut fuer Experimentelle Kernphysik, Universitaet Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)
2. Physikalisches Institut, Universitaet Tuebingen, Auf der Morgenstelle 12, D-72076 Tuebingen (Germany)

The values of the pion nucleon ([pi][ital N]) [sigma] term, as determined, on the one hand, from experimental pion nucleon scattering by means of dispersion relations and, on the other hand, from baryon masses by means of chiral perturbation theory, differ by 10 to 15 MeV. The origin of this discrepancy is not yet understood. If the difference between the two values is attributed to the scalar current of strange sea quark pairs within the proton, the contribution to the proton mass would be of the order of 120 MeV. The discrepancy may hint at either theoretical deficiencies or an inadequate [pi][ital N] database. In order to provide reliable experimental data we have measured angular distributions of elastic pion proton scattering at pion energies [ital T][sub [pi]]=32.2 and 44.6 MeV using the magnet spectrometer LEPS located at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland. From the data covering the region of the Coulomb nuclear interference, the real parts of the isospin-even forward scattering amplitude Re[ital D][sup +]([ital t]=0), have been determined as a function of energy. The results have been compared with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, revealing discrepancies most pronounced for the [pi][sup +][ital p] data. The experimentally determined values for Re[ital D][sup +]([ital t]=0), however, support the KH80 prediction (which is based on [pi][ital N] data available in 1979).

• OSTI ID: 6546930
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Vol. 51:4; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
HYDROGEN 1 TARGET
PION PLUS REACTIONS
SCATTERING AMPLITUDES
ANGULAR DISTRIBUTION
DIFFERENTIAL CROSS SECTIONS
DISPERSION RELATIONS
ISOSPIN
MEV RANGE 10-100
AMPLITUDES
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DISTRIBUTION
ENERGY RANGE
HADRON REACTIONS
MESON REACTIONS
MEV RANGE
NUCLEAR REACTIONS
PARTICLE PROPERTIES
PION REACTIONS
TARGETS
662340* - Hadron Interactions- (1992-)
663110 - General & Average Properties of Nuclei & Nuclear Energy Levels- (1992-)
663460 - Meson- & Hyperon-induced Reactions & Scattering- (1992-)