Development of the TORCH Time-of-Flight Detector

点击翻译按钮获取中文摘要

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.