Baryon QCD sum rules in an external isovector-scalar field and baryon isospin mass splittings
- TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada)
Within the QCD sum-rule approach in an external field, we calculate the baryon matrix element of isovector-scalar current, {ital H}{sub {ital B}}={l_angle}{ital B}{vert_bar}{ital {bar u}u}{minus}{ital {bar d}d}{vert_bar}{ital B}{r_angle}/2{ital M}{sub {ital B}}, for octet baryons, which appears in the response of the correlator of baryon interpolating fields to a constant isovector-scalar external field. The sum rules are obtained for a general baryon interpolating field with an appropriate form for the phenomenological ansatz of the spectral density. The key phenomenological input is the response of the quark condensates to the external field. To first order in the quark mass difference {delta}{ital m}={ital m}{sub {ital d}}{minus}{ital m}{sub {ital u}}, the nonelectromagnetic part of the baryon isospin mass splitting is given by the product of {delta}{ital m} and {ital H}{sub {ital B}}. Therefore, the QCD sum-rule calculation of {ital H}{sub {ital B}} leads to an estimate of the octet baryon isospin mass splittings. The resulting values are comparable to the experimental values; however, the sum-rule predictions for {ital H}{sub {ital B}} are sensitive to the values of the response of the quark condensates to the external source, which are not well determined.
- OSTI ID:
- 115941
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 5 Vol. 52; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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