Elucidating the fundamental nature of hadrons with Particle Identification Detector

在本申请中，我们要求通过CrystalBall@Mami为下一代科学计划提供及时且经济高效的英国设备。这一新的研究图景是由一种新的高速时间投影室(TPC)的调试实现的，它可以用高强度、高能量的光子束运行。TPC将于2022年底建成，实验将于2023年运行。TPC将提供精确的带电粒子跟踪，并将首次使我们能够探测光反应后的低能量反冲核(质子、氚、较重的物质)。后一方面为英国在MAMI打开了令人兴奋的科学可能性，这一新能力与我们最具影响力的研究目标很好地结合在一起。测量方案将提供有关新的d*六夸克粒子基本性质的关键信息。此外，有了TPC，就有了新的和令人兴奋的前景来详细研究d*的介质中相互作用，使用主要的和干净的d*共振峰可以通过核反冲标记访问。正如我们最近表明的那样，六夸克也可能共存于中子星内部，有效地将允许的最大中子星大小限制在LIGO和NICER确定的值。我们还表明，初级产生的六夸克凝聚体可能扮演着暗物质粒子的角色。为了阐述这一概念，我们需要研究核介质中的六夸克行为。它可以在实验室环境中完成，然后将结果应用于中子星的核状态方程。约克领导了一个重大的CB@MAMI计划，旨在使用相干pion光产生的方法精确确定中子皮肤的大小和形状。准确的皮肤测量是核理论的有力鉴别器；DFT和从头计算预测预测的皮肤厚度差异很大，突显出准确的测量将如何为核科学提供关键的缺失信息。中子皮还与核子物质状态方程中最不受约束和最难以捉摸的参数--对称能的密度依赖性有关(L)。TPC允许测量转移到核反冲的动量，大大减少了系统学，大大改善了相干和非相干过程的分离，开辟了新的目标可能性(例如，氙气等惰性气体)，并使后续的反冲核伽马能谱可以排除核分裂带来的不必要背景。

In this application we request a timely and cost-effective UK equipment contribution to next generation science programmes with the CrystalBall@MAMI. This new research landscape is enabled by the commissioning of a new high-rate time projection chamber (TPC) which can operate with intense, energetic photon beams. The TPC will be constructed by the end of 2022 with experiments running in 2023. The TPC will provide charged particle tracking with exquisite accuracy and, for the first time, will allow us to detect low energy recoiling nuclei (protons, deuterons, heavier species) following photoreactions. The latter aspect opens up exciting scientific possibilities for the UK at MAMI and this new capability aligns well with our highest impact research goals. The measurement programme will provide key information on the fundamental properties of the new d* hexaquark particle. Additionally, with the TPC there are new and exciting prospects to study in detail the in-medium interaction of the d*, using the dominant and clean d* resonance peaks accessible with nuclear recoil tagging.As we recently showed, hexaquarks might also coexist inside neutron stars effectively restricting the maximum allowed neutron star size at exactly the value determined by LIGO and NICER. We have also shown that primordinary produced hexaquark condensate might play a role of dark-matter particles. To elaborate this concept, one needs to investigate hexaquark behaviour inside the nuclear medium. It can be done in a laboratory environment, and then apply the results to the nuclear equation of state (EoS) of neutron stars.York leads a major CB@MAMI programme aiming to accurately determine the size and shape of neutron skins, using the method of coherent pion photoproduction. Accurate skin determinations are a powerful discriminator for nuclear theories; DFT and ab-initio predictions predict widely varying skin thicknesses, highlighting how accurate measurements will provide crucial missing information for nuclear science. The neutron skin also correlates with the most poorly constrained and elusive parameter in the EoS for nucleonic matter, the density dependence of the symmetry energy (L). The TPC allows measurement of momentum transfer to the nuclear recoil with greatly reduced systematics, enables much improved separation of coherent and incoherent processes, opens up new target possibilities (e.g. noble gases like Xenon) and for subsequent gamma spectroscopy on the recoil nuclei can veto unwanted backgrounds from nuclear breakup.