1994/02/03 by Stanley J. Brodsky, Felix Schlumpf · 6 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1016/0370-2693(94)90525-8
published as Phys.Lett.B329:111-116,1994 · 17 pages, RevTeX, 4 uuencoded figures, SLAC-PUB-6431
arxiv created 1994/02/03 · openalex publication_date 1994/06/01 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We calculate the proton's magnetic moment μp and its axial-vector coupling gA as a function of its Dirac radius R1 using a relativisitic three-quark model formulated on the light-cone. The relationship between μp and gA is found to be independent of the assumed form of the light-cone wavefunction. At the physical radius R1=0.76 fm, one obtains the experimental values for both μp and gA, and the helicity carried by the valence u and d quarks are each reduced by a factor ≃ 0.75 relative to their non-relativistic values. At large proton radius, μp and gA are given by the usual non-relativistic formulae. At small radius, μp becomes equal to the Dirac moment, as demanded by the Drell-Hearn-Gerasimov sum rule. In addition, as R1 → 0, the constituent quark helicities become completely disoriented and gA → 0.