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A definitive determination of the contribution of multi-photon exchange to elastic lepton-nucleon scattering

多光子交换对弹性轻子-核子散射的贡献的明确确定

基本信息

批准号：
190682471
负责人：
Professor Dr. Reinhard Beck
金额：
--
依托单位：
Helmholtz-Institut für Strahlen- und Kernphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2011
资助国家：
德国
起止时间：
2010-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/190682471?language=en
关键词：
definitive determination contribution multi photon

项目摘要

This project aims at a precision measurement of the e+p/e-p cross section ratio in elastic lepton proton scattering. It will directly test the contribution of multi-photon effects. Recent determinations of the proton electric to magnetic form factor ratio from polarization transfer measurements at JLab indicate an unexpected and dramatic discrepancy with the form factor ratio obtained using the Rosenbluth separation technique in unpolarized cross section measurements. The possible explanation for this discrepancy is a significant contribution of multi-photon exchange beyond the usual one-photon exchange approximation in the calculation of the elastic electron-proton scattering cross section. Since most of our understanding on the structure of the proton and atomic nuclei is based upon lepton scattering analyzed in terms of the single photon approximation, it is essential to definitively verify the contribution of multi-photon exchange. The current, dramatic discrepancy between recoil polarization and Rosenbluth measurements of the proton elastic form factor ratio constitutes a serious challenge to our understanding of the structure of the proton. The widely accepted explanation in terms of multi-photon exchange demands a definitive confirmation. The aim of the OLYMPUS-experiment at DESY is the determination of this contribution with a precision of 1%.

本项目旨在精确测量弹性轻子质子散射的e+p/e-p截面比。它将直接测试多光子效应的贡献。最近确定的质子电磁形状因子比极化转移测量在JLab表明一个意想不到的和戏剧性的差异与形状因子比使用Rosenbluth分离技术在非极化截面测量。这种差异的可能解释是在弹性电子-质子散射截面的计算中，多光子交换超过通常的单光子交换近似的重要贡献。由于我们对质子和原子核结构的大多数理解都是基于单光子近似下的轻子散射分析，因此必须明确验证多光子交换的贡献。目前，反冲极化和Rosenbluth测量质子弹性形状因子比之间的巨大差异对我们理解质子的结构构成了严重的挑战。被广泛接受的多光子交换的解释需要一个明确的确认。在DESY进行的奥林巴斯实验的目的是以1%的精度确定这种贡献。