Elucidating the fundamental nature of hadrons with Particle Identification Detector

在此应用中，我们要求及时和具有成本效益的英国设备与CrystalBall@MAMI下一代科学计划的贡献。这一新的研究领域是通过一个新的高速率时间投影室（TPC）的调试实现的，该室可以使用强有力的光子束进行操作。TPC将于2022年底建成，并于2023年进行实验。TPC将提供精确的带电粒子跟踪，并首次允许我们在光反应后检测低能反冲核（质子，氘，较重的物质）。后一方面为MAMI的英国开辟了令人兴奋的科学可能性，这种新能力与我们最高的影响力研究目标保持一致。测量计划将提供有关新d* 六夸克粒子基本性质的关键信息。此外，与TPC有新的和令人兴奋的前景，详细研究介质中的相互作用的d*，使用占主导地位的和干净的d* 共振峰可与核反冲taging.As我们最近表明，六夸克也可能共存中子星内有效地限制最大允许中子星星的大小，正是由LIGO和NICER确定的值。我们还表明，原寻常产生的六夸克凝聚体可能发挥暗物质粒子的作用。为了详细阐述这个概念，需要研究核介质中的六夸克行为。约克领导了一个主要的CB@MAMI方案，目的是利用相干π介子光生方法精确确定中子皮的大小和形状。精确的皮肤测定是核理论的有力补充; DFT和从头算预测预测了广泛变化的皮肤厚度，突出了精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的EoS中约束最差和最难以捉摸的参数，对称能（L）的密度依赖性相关。TPC允许测量动量转移到核反冲，大大减少了系统性，使相干和非相干过程的分离得到很大改善，开辟了新的目标可能性（例如惰性气体，如氙气），并为随后的γ光谱反冲核可以否决不必要的背景核分裂。

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.