## Abstract

We use distorted wave electron scattering calculations to extract the weak charge form factor F_{W}(q̄), the weak charge radius R_{W}, and the point neutron radius R_{n} of 208Pb from the Lead Radius Experiment (PREX) parity-violating asymmetry measurement. The form factor is the Fourier transform of the weak charge density at the average momentum transfer q̄=0.475 fm^{-}1. We find F_{W}(q̄)=0.204±0. 028(exp)±0.001(model). We use the Helm model to infer the weak radius from F_{W}(q̄). We find R_{W}=5.826±0.181(exp) ±0.027(model)fm. Here the experimental error includes PREX statistical and systematic errors, while the model error describes the uncertainty in R _{W} from uncertainties in the surface thickness σ of the weak charge density. The weak radius is larger than the charge radius, implying a "weak charge skin" where the surface region is relatively enriched in weak charges compared to (electromagnetic) charges. We extract the point neutron radius R_{n}=5.751±0.175(exp)±0.026(model)±0. 005(strange)fm from R_{W}. Here there is only a very small error (strange) from possible strange quark contributions. We find R_{n} to be slightly smaller than R_{W} because of the nucleon's size. Finally, we find a neutron skin thickness of R_{n}-R_{p}=0.302±0. 175(exp)±0.026 (model) ± 0.005 (strange) fm, where R_{p} is the point proton radius.

Original language | English |
---|---|

Article number | 032501 |

Journal | Physical Review C - Nuclear Physics |

Volume | 85 |

Issue number | 3 |

DOIs | |

State | Published - 26 Mar 2012 |

Externally published | Yes |