{"title":"Proton charge radius from electron scattering","authors":"I. Sick","doi":"10.3390/atoms6010002","DOIUrl":null,"url":null,"abstract":"The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G(q)$ needed for the extrapolation. This shape of $G(q<q_{min})$ is closely related to the shape of the charge density $\\rho (r)$ at large radii $r$, a quantity which is ignored in most analyses. When using our {\\em physics} knowledge about this large-$r$ density together with the information contained in the high-$q$ data, the model dependence of the extrapolation is reduced and different parameterizations of the pre-2010 data yield a consistent value for $R = 0.887 \\pm 0.012fm$. This value disagrees with the more precise value $0.8409 \\pm 0.0004 fm$ determined from the Lamb shift in muonic hydrogen.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":"6 2 1","pages":"2"},"PeriodicalIF":0.0000,"publicationDate":"2017-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"29","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv: Nuclear Experiment","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3390/atoms6010002","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 29
Abstract
The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G(q)$ needed for the extrapolation. This shape of $G(q
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