Abstract
Abstract TORCH is a time-of-flight detector, designed to provide charged π ∕ K particle identification up to a momentum of 10 GeV/c for a 10 m flight path . To achieve this level of performance, a time resolution of 15 ps per incident particle is required. TORCH uses a plane of quartz of 1 cm thickness as a source of Cherenkov photons , which are then focussed onto square Micro-Channel Plate Photomultipliers (MCP-PMTs) of active area 53 × 53 mm 2 , segmented into 8 × 128 pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT and associated readout electronics has been successfully operated in a 5 GeV/c mixed pion/proton beam at the CERN PS facility. Preliminary results indicate that a single-photon resolution better than 100 ps can be achieved. The expected performance of a full-scale TORCH detector for the Upgrade II of the LHCb experiment is also discussed.
Highlights
The TORCH (Time Of internally Reflected CHerenkov light) detector will measure the time-of-flight (ToF) of charged particles over large areas, with the aim to provide Particle IDentification (PID) of pions, kaons and protons up to 10 GeV/c momentum and beyond [1]
The difference in ToF between pions and kaons over a ∼10 m flight path at 10 GeV/c is 35 ps, to achieve positive identification of kaons, TORCH aims for a time resolution of ∼10–15 ps per track
A specific application of TORCH is for the LHCb Upgrade II experiment, where the detector would occupy an area of 30 m2 in front of the current RICH 2 detector [2]
Summary
The TORCH (Time Of internally Reflected CHerenkov light) detector will measure the time-of-flight (ToF) of charged particles over large areas, with the aim to provide Particle IDentification (PID) of pions, kaons and protons up to 10 GeV/c momentum and beyond [1]. The difference in ToF between pions and kaons over a ∼10 m flight path at 10 GeV/c is 35 ps, to achieve positive identification of kaons, TORCH aims for a time resolution of ∼10–15 ps per track. Cherenkov photons travel to the periphery of the quartz plates by total internal reflection where they are reflected by a cylindrical mirror surface of a quartz block. This focuses the photons onto a plane of pixellated Micro-Channel Plate Photomultipliers (MCP-PMTs) where their positions and arrival times are measured. A ∼1 mrad precision is required on the measurement of the angles in both planes to achieve the required intrinsic timing resolution [1]
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