Many-Body Currents and the Strange-Quark Content of 4he

Abstract

Meson-exchange current (MEC) contributions to the parity-violating (PV) asymmetry for elastic scattering of polarized electrons from ${}^4$He are calculated over a range of momentum transfer using Monte Carlo methods and a variational ${}^4$He ground state wavefunction. The results indicate that MEC's generate a negligible contribution to the asymmetry at low-$|\qv|$, where a determination of the nucleon's mean square strangeness radius could be carried out at CEBAF. At larger values of momentum transfer -- beyond the first diffraction minimum -- two-body corrections from the $\rho$-$\pi$ \lq\lq strangeness charge" operator enter the asymmetry at a potentially observable level, even in the limit of vanishing strange-quark matrix elements of the nucleon. For purposes of constraining the nucleon's strangeness electric form factor, theoretical uncertainties associated with these MEC contributions do not appear to impose serious limitations.

arXiv comment32 TEX pages and 7 figures (not included, available from authors upon request), CEBAF Preprint #TH-94-10

References in corpus (5)

• Intermediate-Energy Semileptonic Probes of the Hadronic Neutral Current
• Stranger Still: Kaon Loops and Strange Quark Matrix Elements of the Nucleon
• Just How Strange? Loops, Poles and the Strangeness Radius of the Nucleon
• Meson-Exchange Currents and the Strangeness Radius of 4he
• Non-Standard Physics and Nucleon Strangeness in Low-Energy PV Electron Scattering

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