OLYMPUS and TREK: Two Precision Experiments to Determine the Two-Photon Exchange Effect in Lepton-Proton Scattering and to Search for New Physics Beyond the Standard Model

该奖项由2009年美国复苏和再投资法案（公法111-5）资助。Rosenbluth和反冲极化方法之间质子电磁形状因子比测量结果的差异被解释为以前忽略的双光子交换（TPE）效应。 TPE的证据可以通过比较正电子-质子和电子-质子弹性截面来直接和最严格地测试，因为它们的差异与TPE幅度成正比。 如果没有明确的实验测试，不仅电磁形状因子，而且通常在单光子交换框架内完成的所有电子散射数据的解释都受到相当大的怀疑。汉堡DESY的OLYMPUS实验，德国提出通过精确测量正电子-质子与电子-质子的比值来确定弹性轻子-质子散射中的双光子交换效应。质子弹性非极化截面 它利用储存环DORIS（一个内部非极化氢气靶）和麻省理工学院贝茨直线加速器中心的BLAST探测器上的强正电子和电子束。将在汉普顿大学建造以气体电子倍增器技术为基础的前向角跟踪望远镜，作为光度监测器，以加强该装置。预计新的GEM探测器的开发将适用于Jefferson实验室和日本J-PARC的未来实验。拟议的研究计划为国内外一流的教育和研究目的提供了很好的机会。该提案将在汉普顿大学校园内建立一个新的实验室，并为少数民族学生（主要是非洲裔美国人）提供新的研究和教育机会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The observed discrepancy in measurements of the proton electric-to-magnetic form factor ratio between the Rosenbluth and recoil polarization method has been interpreted as due to previously neglected effects of two-photon exchange (TPE). Evidence for TPE can be directly and most stringently tested by comparison of positron-proton and electron-proton elastic cross sections, as their difference is proportional to the TPE amplitude. Without a definitive experimental test, not only the electromagnetic form factors but also the interpretations of all electron scattering data, usually done in the framework of single-photon exchange, are under considerable doubt.The OLYMPUS experiment at DESY, Hamburg, Germany has been proposed to definitively determine the effect of two-photon exchange in elastic lepton-proton scattering by precisely measuring the ratio of positron-proton to electron-proton elastic unpolarized cross sections. It makes use of intense beams of positrons and electrons at the storage ring DORIS, an internal unpolarized hydrogen gas target, and the BLAST detector from the MIT-Bates Linear Accelerator Center. The setup will be augmented with forward-angle tracking telescopes based on gas electron multiplier (GEM) technology, to be used as luminosity monitors, which will be constructed at Hampton University. It is anticipated that development of new GEM detectors will be applicable in future experiments at Jefferson Lab and at J-PARC in Japan.The proposed research program offers great opportunity for first class education and research purpose domestically and abroad. This proposal will lead to a new lab on the campus of Hampton University and opens new research and educational opportunities for students from minority populations, predominantly African-Americans.