Weak Electric Form Factors Research Articles

Polarization observables and T-noninvariance in the weak charged current induced electron proton scattering

In this work, we have studied the total scattering cross section ($\sigma$), differential scattering cross section ($d\sigma/dQ^2$) as well as the longitudinal ($P_L(E_e,Q^2)$), perpendicular ($P_P(E_e,Q^2)$), and transverse ($P_T(E_e,Q^2)$) components of the polarization of the final hadron ($n$, $ \Lambda$ and $\Sigma^0$) produced in the electron proton scattering induced by the weak charged current. We have not assumed T-invariance which allows the transverse component of the hadron polarization perpendicular to the production plane to be non-zero. The numerical results are presented for all the above observables and their dependence on the axial vector form factor and the weak electric form factor are discussed. The present study enables the determination of the axial vector nucleon-hyperon transition form factors at high $ Q^2$ in the strangeness sector which can provide test of the symmetries of the weak hadronic currents like T-invariance and SU(3) symmetry while assuming the hypothesis of conserved vector current and partial conservation of axial vector current.

THE STRANGENESS CHANGING ANTINEUTRINO REACTION ${\bar\nu}_L+P\longrightarrow\Lambda+L^+$

We obtain the cross sections for the reactions [Formula: see text] where L is a massive lepton, i.e. a muon or a tau lepton. We do this from near threshold to relativistic energies. We further obtain the contributions of various form factors and interference terms to the cross section with a view to discovering if the contributions from hard to observe form factors such as the weak pseudoscalar form factor, FP, and the weak electric form factor, FE might be obtained via these reactions. The form factor FE is particularly interesting as in the more usually observed p↔n transition it is a second class current and forbidden by G-parity. However in the p↔Λ transition it is not forbidden and it would be desirable to learn if it is present. Finally we discuss our results and prospects for these experiments.

Strange-baryon production via charge-changing weak currents in high-energy electron-capture reactions.

We investigate strange-baryon \ensuremath{\Lambda} and ${\ensuremath{\Sigma}}^{0}$ production via charge-changing weak currents on a proton target induced by high-energy electrons. To evaluate the various weak form factors, including vector, weak-magnetism, and scalar form factors for the polar-vector current and the axial-vector, pseudoscalar, and weak electric form factors for the axial-vector current, we adopt the flavor-SU(6) wave functions with quarks described as confining Dirac particles. The quark wave function adopted is of the form given by the MIT bag model, with or without the sharp surface smoothed out. In the few-GeV range, it is found that the cross section for large-angle \ensuremath{\Lambda} production is in the range of ${10}^{\mathrm{\ensuremath{-}}40}$ ${\mathrm{cm}}^{2}$ while that for ${\ensuremath{\Sigma}}^{0}$ is smaller by about an order of magnitude. The cross section is sensitive to contributions due to vector, weak-magnetism, and axial-vector form factors. Measurements of these form factors in the few-GeV range provide tests of quark models for nucleons and strange baryons. Some important aspects, such as recoil effects, are briefly discussed.

Delta (1232) production via charge-changing weak currents: e

We investigate ..delta..(1232) production via charge-changing weak currents e/sup -/+p..--> delta../sup 0/+..nu../sub e/ and e/sup +/+p..--> delta../sup ++/+nu-bar/sub e/ at electron/positron beam energies in the range of a few GeV. A general formalism is introduced for the N..--> delta.. transition form factors, including the weak magnetism, weak quadrupole, and weak scalar form factors for the polar-vector current and the axial, pseudoscalar, recoil, and weak electric form factors for the axial current. The form factors related to the polar-vector current are related to ..delta..(1232) electroproduction on a nucleon target. For nucleons and deltas, we adopt in this calculation the flavor SU(6) wave functions, with quarks described as confined Dirac particles. The quark wave function adopted is of the form given by the MIT bag model, with or without the sharp boundary smoothened out. In the few GeV range, it is found that cross sections can be as large as 10/sup -38/ cm/sup 2/ and are sensitive to induced form factors such as the weak magnetism form factor. It is also found that, for a beam energy of around 4.0 GeV, the predicted cross sections depend sensitively on whether or not the sharp boundary in the quark wave function is smoothened out.

Quark-model calculation of the weak electric coupling in semileptonic baryon decay

The weak electric form factor ${g}_{2}$ is calculated in the nonrelativistic quark model (NRQM) and the MIT bag model for weak $\ensuremath{\Delta}S=1$ semileptonic transitions. The bag-model result is $\frac{{g}_{2}}{{g}_{1}}=0.30$ with the NRQM result roughly twice this. Other weak transition form factors are tabulated, including expected SU(3)-breaking effects.