Development of the TORCH Time-of-Flight Detector

该提案描述了一个为期两年的研究和开发计划，旨在开发一个名为TORCH的飞行时间（ToF）探测器，用于未来的粒子物理实验。TORCH使用了一种新技术来测量带电粒子穿过它的到达时间。由于ToF与粒子的速度成正比，因此可以通过粒子在实验磁场中的弯曲来测量粒子的动量，从而确定粒子的类型（π介子、质子或K介子）。TORCH使用10 mm厚的石英平面作为切伦科夫光源。当带电粒子穿过介质时，粒子的速度超过介质中的光的速度时，光子被发射。在石英板中辐射的光子通过全内反射传播到板的顶部边缘，然后聚焦到微通道板（MCP）光子检测器阵列上。ToF分辨率优于15 ps/轨道，这将导致π/K/p粒子分离高达10 GeV/c及以上的动量。TORCH模块将由石英辐射棒和聚焦块构成，MCP探测器将安装在该模块上。然后，该模块将在CERN的带电粒子束中进行测试。将编写软件来重建探测到的光子，评估它们的到达时间，然后计算辐射它们的入射粒子的飞行时间。TORCH随后将被转移到LHCb实验，进行完整的系统测试，以验证带电轨道和光子的计时能力。这项研究将带来几个重要的好处。TORCH探测器将具有独特的能力，为粒子识别（PID）至关重要的实验提供ToF。例如，LHCb升级是一个所谓的味道物理实验，它在很大程度上依赖于区分碰撞中所有粒子的能力。此外，未来在FCC-ee机器上进行的实验，被提议作为LHC之后可能的欧洲加速器，也将从TORCH促进的紧凑空间体积中进行的PID测量中受益匪浅。TORCH也可以用于ToF探测器，它将带电粒子和高能伽马与它们起源的主要碰撞点（顶点）相关联，将它们的来源与LHC束团交叉中存在的几个顶点区分开来。未来味道物理实验的一个关键物理目标是了解CP破坏的起源，CP破坏仍然是实验粒子物理学的奥秘之一，也是宇宙中物质-反物质不对称性难题的关键部分。新一代的实验将利用大量的B-强子（含有b-夸克的粒子），以研究罕见的B-强子衰变的物质-反物质不对称性。因此，TORCH将使新的和意想不到的物理学的研究成为可能，这可能代表着我们对自然的理解向前迈出了一大步。最后，TORCH的建议在很大程度上依赖于新型MCP光子探测器的研发，这些探测器是由TORCH与工业界合作开发的。MCP已经被量化为具有良好的寿命、出色的定时分辨率（~20-30皮秒）和空间精度。MCP是用于粒子物理学、天体粒子物理学实验以及空间和地基天文学项目的有前途的探测器。它们也在医学成像中有应用，例如。正电子发射断层摄影（PET）以及许多其他需要以良好的空间精度和定时检测低水平光的应用。

This proposal describes a two-year research and development programme towards developing a time-of-flight (ToF) detector, named TORCH, for future particle physics experiments. TORCH uses a novel technique to measure the arrival time of a charged particle which passes through it. Because the ToF is proportional to the particle's velocity, the particle type (pion, proton or kaon) can be determined from knowledge of the particle's momentum, measured from the particle's bend in the experiment's magnetic field. TORCH uses a plane of 10 mm thick quartz as a source of Cherenkov light. The photons are emitted when a charged particle traverses a medium in which the particle's velocity exceeds that of light in the medium. The photons radiated in the quartz plate propagate by total internal reflection to the top edge of the plate and are then focused onto an array of Micro-Channel Plate (MCP) photon detectors. A ToF resolution of better than 15 ps per track is to be achieved, which will result in a pi/K/p particle separation up to a momentum of 10 GeV/c and beyond.A TORCH module will be constructed from a quartz radiator bar and focussing block, to which the MCP detectors will be mounted. The module will then be tested in a charged particle beam at CERN. Software will be written to reconstruct the detected photons, to evaluate their arrival times, and then to calculate the time of flight of the incident particle which radiated them. TORCH will then be moved to the LHCb experiment, to perform a full system test to verify the timing capabilities for charged tracks and photons.There are several important benefits that this research will bring. The TORCH detector will have a unique capability to provide ToF to experiments where particle identification (PID) is paramount. As an example, the LHCb Upgrade is a so-called flavour-physics experiment which relies heavily on the ability to distinguish all particles in the collision. Also, future experiments at the FCC-ee machine, proposed as a possible European accelerator after the LHC, would also highly benefit from PID measurements made in a compact spatial volume that TORCH facilitates. TORCH can also be used for a ToF detector which will associate charged particles and high-energy gammas with the primary collision point (vertex) from which they originate, differentiating their source from the several vertices present in the crossing of LHC beam bunches. A key physics aim of future flavour-physics experiments is to understand the origin of CP violation, which remains one of the mysteries of experimental particle physics and is a key piece in the puzzle of the matter-antimatter asymmetry in the universe. New generations of experiments will exploit the large number of B-hadrons (particles containing a b-quark), produced in order to investigate matter-antimatter asymmetries of rare B-hadron decays. Hence TORCH will enable the study of new and unexpected physics, and which can represent a huge step forward in our understanding of nature. Finally, the TORCH proposal relies heavily on the R&D of novel MCP photon detectors, which are developed by TORCH in collaboration with industry. The MCPs have been quantified for their good lifetime, excellent timing resolution (~20-30 picoseconds) and spatial accuracy. The MCPs are promising detectors for use in particle physics, astro-particle physics experiments, and also space and ground-based astronomy projects. They also have applications in medical imaging, eg. positron emission tomography (PET), and many other applications that require detection of low levels of light with good spatial accuracy and timing.