Hadron Spectroscopy using Polarized Photons

使用偏振光子的强子能谱

• 批准号: 0969434
• 负责人: Franz Klein
• 金额: $ 49.5万
• 依托单位: Catholic University of America
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0969434&HistoricalAwards=false
• 关键词: Hadron; Spectroscopy; using; Polarized; Photons

The scattering of high energy photons on protons has been studied for many decades. The long interest in this endeavor is largely motivated by the study of nucleon and meson excitations, which manifest themselves as specific configurations of quarks inside the nucleon. With the development of high energy, highly-polarized photon beams and ultra-cold polarized targets, which keep the orientation of the nucleon spin frozen at a few milliKelvin, we finally are able to measure all components of the scattering amplitudes in the form of polarization observables, and thus to disentangle unambiguously the resonant contributions to the scattering. CUA is a leading institution in this program that is being conducted in Hall B at the Thomas Jefferson National Accelerator Facility (JLab) in Newport News, VA. Two CUA graduate students are extracting all polarization observables for the interaction of photons and protons in which so-called strange particles are produced, particles that do not occur in nature but only in high-energy scattering. Their research builds the corner stone of the program.The excitation of the glue that holds quarks and antiquarks closely together in mesons is predicted by the theory of strong interaction but has not experimentally been established. The GlueX experiment being constructed at JLab will be devoted to the search for such excitations. By using a high energy, highly polarized photon beam and a high-resolution detector with complete coverage, the GlueX experiment is expected to settle the question. CUA's contribution to the experiment is the construction and maintenance of the broad-band tagging hodoscope and the polarized photon source. The construction project provides excellent research opportunities for CUA's undergraduate students in physics and engineering who will be guided to take over key roles in prototyping, constructing and testing the hodoscope. The grant provided by NSF will support CUA's efforts in the frozen-spin target program in JLab's Hall B as well as the GlueX construction project.

高能光子在质子上的散射已经研究了几十年。对这一努力的长期兴趣主要是由对核子和介子激发的研究激发的，它们表现为核子内部夸克的特定构型。随着高能、高偏振光子束和超冷偏振靶的发展，使核子自旋的方向保持在几毫开尔文，我们最终能够以偏振观测值的形式测量散射振幅的所有分量，从而明确地解开共振对散射的贡献。该项目在弗吉尼亚州纽波特纽斯的托马斯·杰斐逊国家加速器设施（JLab）的B厅进行。两名CUA研究生正在提取所有可观测到的光子和质子相互作用的偏振，在这种相互作用中产生了所谓的奇怪粒子，这种粒子不存在于自然界中，只存在于高能散射中。他们的研究奠定了这个项目的基石。强相互作用理论预测了介子中将夸克和反夸克紧密结合在一起的胶的激发，但尚未在实验中得到证实。JLab正在进行的GlueX实验将致力于寻找这样的激发。通过使用高能、高偏振光子束和全覆盖的高分辨率探测器，GlueX实验有望解决这个问题。CUA对实验的贡献是宽带标记hodoscope和偏振光子源的构建和维护。该建设项目为我校物理系和工程系的本科生提供了极好的研究机会，他们将被引导承担hodoscope原型设计、建造和测试的关键角色。由NSF提供的赠款将支持CUA在JLab B厅的冷冻自旋目标项目以及GlueX建设项目中的努力。