Weak charge form factor and radius of 208Pb through parity violation in electron scattering

<p>We use distorted wave electron scattering calculations to extract the weak charge form factor FW(q¯), the weak charge radius RW, and the point neutron radius Rn 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 q¯=0.475 fm−1. We find FW(q¯)=0.204±0.028(exp)±0.001(model). We use the Helm model to infer the weak radius from FW(q¯). We find RW=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 RW 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 Rn=5.751±0.175(exp)±0.026(model)±0.005(strange)fm fromRW. Here there is only a very small error (strange) from possible strange quark contributions. We find Rn to be slightly smaller than RW because of the nucleon's size. Finally, we find a neutron skin thickness of Rn−Rp=0.302±0.175(exp)±0.026 (model) ± 0.005 (strange) fm, where Rp is the point proton radius.</p

Arguing About Art : Contemporary Philosophical Debates

This revised and expanded anthology comprises 27 essays on contemporary aesthetics, reflecting a broad range of perspectives from philosophy, art history, contemporary art and popular culture. The book is divided into 12 sections: food as art, authenticity in musical performance, forgery in painting, rock music and culture, the aesthetic appreciation of nature, photography and representation, fiction and emotions, enjoying horror movies/novels, sentimentality, art and morality, feminism and aesthetics, public art (focusing on Richard Serra and Maya Lin). Each section features essays that present diverse points of view on a given topic, providing a dialogical model for the practice of philosophical debate. The editors' introductory texts for each section highlight central questions raised in the essays. Includes suggestions for further reading on each topic. Index. 475 bibl. ref