Calculation of {l_angle}{ital p}{vert_bar}{ital {bar u}u}{minus}{ital {bar d}d}{vert_bar}{ital p}{r_angle} from QCD sum rules and the neutron-proton mass difference
- Department of Physics and Center for Theoretical Physics, University of Maryland, College Park, Maryland 20742 (United States)
- Center for Theoretical Studies, Institute of Science, Bangalore, 560012 (India)
The proton matrix element of the isovector-scalar density, {l_angle}{ital p}{vert_bar}{ital {bar u}u}{minus}{ital {bar d}d}{vert_bar}{ital p}{r_angle}/2{ital M}{sub {ital p}}, is calculated by evaluating the nucleon current correlation function in an external isovector-scalar field using the QCD sum-rule method. In addition to the usual chiral and gluon condensates of the QCD vacuum, the response of the chiral condensates to the external isovector field enters the calculation. The latter is determined by two independent methods. One relates it to the difference between the up and down quark chiral condensates and the other uses the chiral perturbation theory. 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 neutron-proton mass difference is given by the product {delta}{ital m}{l_angle}{ital p}{vert_bar}{ital {bar u}u}{minus}{ital {bar d}d}{vert_bar}{ital p}{r_angle}/2{ital M}{sub {ital p}}; the resulting value is in reasonable agreement with the experimental value.
- Research Organization:
- University of Maryland
- DOE Contract Number:
- FG02-93ER40762
- OSTI ID:
- 26051
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 7 Vol. 51; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
Similar Records
{pi}{ital N}{sigma} term, {ital {bar s}}{ital s} in the nucleon, and the scalar form factor: A lattice study
Estimates of [ital m][sub [ital d]][minus][ital m][sub [ital u]] and [l angle][ital [bar d]d][r angle][minus][l angle][ital [bar u]u][r angle] from QCD sum rules for [ital D] and [ital D][sup *] isospin mass differences