MRI Consortium: Development of a Forward Calorimetry Upgrade for the STAR Detector

量子色动力学，或QCD，被认为是现代物理学的基石。作为核力的基本理论，它描述了通过被称为胶子的无质量粒子交换而结合在一起的点状夸克的强相互作用物质。然而，尽管它在解释在最高能量下进行的测量方面取得了显著的成功，但对低能量现象的详细理解，例如构成宇宙可见质量的99%的质子和中子的内部结构，在理论上仍然难以捉摸，必须通过实验来获得。在过去的几十年里，在这一领域已经取得了很大的进展，但对于质子中能量很低或很高的成分来说，进展还不是很大。该项目将升级恒星探测器，以便能够研究质子-质子碰撞产物的远前角，这是一种由高动量夸克散射在低动量胶子上主导的运动学制度。这项研究将为探索夸克、胶子及其自旋在空间和动量中的分布提供一个独特的机会。在质子-核碰撞中使用相同的技术将有助于更好地理解质子和中子的性质在核环境中是如何改变的。这反过来将提高对核-核碰撞的理解。恒星前进升级旨在探索部分子动量分数的很高和很低区域的QCD物理，到目前为止，这一运动学制度在RHIC仍然无法获得。它将在伪快度范围2.5-4范围内为中性介子、光子、电子、喷流和领先强子提供卓越的探测和重建能力。为了降低成本和风险，探测器组件的大部分将由以前使用过的部件组成。电磁量热计将使用翻新的采样铅闪烁体模块从PHENIX。强子量热计将是一种夹层铁闪烁板采样型，由单独的研发基金设计和制作原型。这两个热量计将共享相同的高性价比读出电子设备，并将使用SiPM作为光传感器，从而使它们能够在没有屏蔽的情况下在高磁场和高辐射环境中运行，就像在这个地点遇到的那样。根据设计，该系统是可扩展和可重新配置的：EMCal区块只需垂直堆叠，而HCal“平板”将就地组装。整合到STAR只需要对现有基础设施进行最小程度的修改。基于详细的GEANT模拟，正向量热系统(FCS)将具有非常好的电磁(10%/Sqrt(E)+3%)和强子(~50%/Sqrt(E)+10%)能量分辨率。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum Chromodynamics, or QCD, is considered a cornerstone of modern physics. As the fundamental theory of the nuclear force, it describes strongly interacting matter in terms of point-like quarks bound together via exchange of massless particles called gluons. Yet despite its remarkable success in explaining measurements carried out at the highest energies, a detailed understanding of low-energy phenomena, such as the internal structure of the protons and neutrons that make up 99% of the visible mass of the universes, remains elusive theoretically and must be gained through experiment. Over the last few decades, much progress has been made in this area, but not for the very low or very high energy constituents within the proton. This project will upgrade the STAR detector in order to make possible the study of proton-proton collision products at far-forward angles, a kinematic regime dominated by the scattering of high-momentum quarks on low-momentum gluons. This study will provide a unique opportunity to explore how the quarks, gluons, and their spins are distributed in space and momentum. Using the same techniques in proton-nucleus collisions will allow for a better understanding of how properties of protons and neutrons are modified in the nuclear environment. That in turn will improve the understanding of nucleus-nucleus collisions.The STAR forward upgrade is designed to explore QCD physics in the very high and low regions of partonic momentum fraction, a kinematic regime that has thus far remained inaccessible at RHIC. It will provide superior detection and reconstruction capabilities for neutral pions, photons, electrons, jets, and leading hadrons over the pseudo-rapidity range 2.5-4. To reduce costs and risk, much of the detector package will consist of previously used components. The electromagnetic calorimeter will use refurbished sampling Pb-scintillator blocks from PHENIX. The hadronic calorimeter will be a sandwich iron-scintillator plate sampling type, designed and prototyped with separate R&D funds. Both calorimeters will share the same cost-effective readout electronics, and will use SiPMs as photo-sensors, thereby allowing them to operate without shielding in high magnetic fields and high radiation environments, as will be encountered in this location. By design, the system is scalable and reconfigurable: the EMCal blocks are simply stacked vertically, while HCal "slabs" will be assembled in place. Integration into STAR will require only minimal modification of existing infrastructure. Based on detailed GEANT simulations, the Forward Calorimetry System (FCS) will have very good electromagnetic (10% / sqrt(E) + 3%) and hadronic (~50% / sqrt(E) + 10%) energy resolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.