Threshold Electropion Production from Current Algebra and Partially Conserved AxialVector Current
Abstract
Threshold electropion production on nucleons, e+N>e+N+π, is studied by currentalgebra techniques using the hypothesis of partially conserved axialvector current, which have proved useful in describing lowenergy mesonbaryon elastic scattering and photopion production on nucleons. The electric and longitudinal multipole moments E_{0+} and L_{0+} are calculated at threshold in terms of the form factors of the electromagnetic and weak axialvector currents. The experimental upper bounds on the slope of the differential cross section as a function of q, the momentum in the πN c.m. system, i.e., (1q) (d^{2}σdΩdS_{20}^{L}), where S_{20}^{L} is the laboratory energy of the final electron, are sufficiently strong to relate the form factors for various values of k^{2}, the momentum transfer squared of the electrons. More precisely, in this way one can relate the neutron charge form factor G_{e}^{n}(k^{2}) to normalized axialvector form factor F_{A}(k^{2}). If one takes F_{A}(k^{2}) to have the dipole form F_{A}(k^{2})=(1+k^{2}M_{A}^{2})^{2} with M_{A}^{2}=1.42 BeV^{2}, which is given by arguments based on chiral SU(2)×SU(2) and consistent with recent neutrino experiments, then the resulting values of G_{e}^{n}(k^{2}) in the range considered, 0.2<=k^{2}<=0.6 BeV^{2}, are consistent with information about G_{e}^{n}(k^{2}) from electrondeuteron and thermalneutronelectron scattering.
 Publication:

Physical Review
 Pub Date:
 September 1968
 DOI:
 10.1103/PhysRev.173.1708
 Bibcode:
 1968PhRv..173.1708G