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Up-down quark mass difference: Couplings of pions to nucleons or isobars and low-energy nucleon-nucleon scattering

Journal Article · · Phys. Rev. C; (United States)
We investigate effects of the up-down quark mass difference on the couplings of pions to nucleons or isobars. The calculated ..pi..NN and ..pi..N..delta.. couplings are used to derive the long-range one-pion-exchange potential and the intermediate-range attraction for the three different cases: p-p, p n-p, and n-n. The resultant potentials are then used to determine numerically the low-energy scattering parameters, including both the scattering length a and the effective range r. Our results indicate that a reasonable up-down quark mass difference such as 10 MeV yields a value for Vertical Bara/sub pp/Vertical Bar-Vertical Bara/sub nn/Vertical Bar of about +0.6 fm, which is sizable from the experimental point of view. Our results also suggest that the large observed value for Vertical Bara/sub np/Vertical Bar-Vertical Bara/sub nn/Vertical Bar can be understood primarily as a manifestation of the pion mass difference.
Research Organization:
Indiana University Cyclotron Facility and Nuclear Theory Center, Department of Physics, Indiana University, Bloomington, Indiana 47405
OSTI ID:
5198803
Journal Information:
Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 29:1; ISSN PRVCA
Country of Publication:
United States
Language:
English