Isospin-breaking corrections to nucleon electroweak form factors in the constituent quark model

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · Physical Review, C

DOI:https://doi.org/10.1103/PhysRevC.52.1061· OSTI ID:112958

Dmitrasinovic, V; Pollock, S J ^[1]

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1. Nuclear Physics Laboratory, Physics Department, University of Colorado, P.O. Box 446, Boulder, Colorado 80309 (United States)

We examine isospin breaking in the nucleon wave functions due to the {ital u}{minus}{ital d} quark mass difference and the Coulomb interaction among the quarks, and their consequences on the nucleon electroweak form factors in a nonrelativistic constituent quark model. The mechanically induced isospin breaking in the nucleon wave functions and electroweak form factors are exactly evaluated in this model. We calculate the electromagnetically induced isospin admixtures by using first-order perturbation theory, including the lowest-lying resonance with nucleon quantum numbers but isospin 3/2. We find a small ({le} 1%), but finite correction to the anomalous magnetic moments of the nucleon stemming almost entirely from the quark mass difference, while the static nucleon axial coupling remains uncorrected. Corrections of the same order of magnitude appear in charge, magnetic, and axial radii of the nucleon. The correction to the charge radius in this model is primarily isoscalar, and may be of some significance for the extraction of the strangeness radius from, e.g., elastic forward angle parity violating electron-proton asymmetries, or elastic {sup 4}He({bold e},{ital e}{prime}) experiments.

• OSTI ID: 112958
• Journal Information: Physical Review, C, Journal Name: Physical Review, C Journal Issue: 2 Vol. 52; ISSN PRVCAN; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CORRECTIONS
COULOMB FIELD
COUPLING
FORM FACTORS
ISOSPIN
MAGNETIC MOMENTS
NUCLEONS
PERTURBATION THEORY
QUANTUM NUMBERS
QUARK MODEL
STRANGENESS
WAVE FUNCTIONS