Mapping the Spectrum of Light Quark Mesons and Gluonic Excitations with Linearly Polarized Photons

点击翻译按钮获取中文摘要

Subatomic physics seeks to understand nature - and all its laws - at the most fundamental level, down to its elementary constituents and their interactions. Tremendous strides have been made in the last several decades, using accelerators and astrophysical observations, which have strengthened our conviction that the basic model, known as the Standard Model, is essentially a valid description of the subatomic world but not necessarily a complete one. Its success is based fundamentally on the concept of “asymptotic freedom,” which stipulates that the quarks, the most elemental particles, behave as free particles when their separation distance is small (such as in high energy collisions) so that analytical calculations of their weakened interactions can be made. However, when the quarks are bound together to form ordinary matter their interactions are so strong that they cannot be separated and cannot exist as individual free quarks. This is an experimental fact that imposes an additional aspect to the Standard Model, that of “quark confinement.” Its exact nature remains one of the outstanding problems in physics. In the confinement regime, where analytical calculations are not feasible, models have to be constructed with the freedom to adjust inputs, as required by experimental data, in order to learn about fundamental aspects of the problem at hand. For this to lead to a solid understanding of the true nature of confinement, high quality and reliable experimental data are absolutely necessary. The physics goal of the GlueX experiment, then, is to create and identify exotic forms of matter that, by their very nature, exhibit unique signatures among all other particles that will allow theoretical models of confinement to be tested in a most constraining way possible. This is a difficult task requiring experimental conditions that are just now becoming possible in accelerator and detector technology. In particular, the latter has benefited from the recent development of large photo sensors that are completely immune to magnetic fields present in these types of experiments. Our group played a defining role in guiding industry towards the development of these devices and they are now available commercially to the subatomic, medical and nuclear safety fields.