Abstract
The TORCH time-of-flight detector is designed to provide particle identification in the momentum range 2−10GeV∕c over large areas. The detector exploits prompt Cherenkov light produced by charged particles traversing a 10mm thick quartz plate. The photons propagate via total internal reflection and are focused onto a detector plane comprising position-sensitive Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a single-photon timing resolution of 70ps, giving a timing precision of 15ps per charged particle by combining the information from around 30 detected photons. The MCP-PMT detectors have been developed with a commercial partner (Photek Ltd, UK), leading to the delivery of a square tube of active area 53×53mm2 with a granularity of 8×128pixels equivalent. A large-scale demonstrator of TORCH, having a quartz plate of dimensions 660×1250×10mm3 and read out by a pair of MCP-PMTs with custom readout electronics, has been verified in a test beam campaign at the CERN PS. Preliminary results indicate that the required performance is close to being achieved. The anticipated performance of a full-scale TORCH detector at the LHCb experiment is presented.
Highlights
TORCH is a Time of Flight (ToF) detector which aims to improve low momentum (2–10 GeV∕c) Particle Identification (PID) for the LHCb experiment [1,2]
When a charged particle passes through the 10 mm thick radiator plate, Cherenkov photons are generated and subsequently trapped by total internal reflection, some travelling to the top of the plate
A half-sized TORCH module with a 660 × 1250 × 10 mm3 radiator plate has been tested in an 8 GeV∕c mixed proton–pion beam at the CERN PS
Summary
TORCH is a Time of Flight (ToF) detector which aims to improve low momentum (2–10 GeV∕c) Particle Identification (PID) for the LHCb experiment [1,2]. The position and time of arrival of the Cherenkov photons are measured by custom-designed MicroChannel Plate Photo-Multiplier Tubes (MCP-PMTs) [3] developed by Photek Ltd (UK). These are square tubes of active area 53 × 53 mm with a granularity of 8 × 128 pixels-equivalent, in x and y′ respectively, read out by electronics employing the NINO and HPTDC chipsets [4,5]. TORCH is proposed for the Upgrades Ib and II of the LHCb detector and will consist of eighteen 660 × 2500 × 10 mm modules positioned approximately 9.5 m from the interaction region Over this distance, the difference in time of flight between pions and kaons at 10 GeV∕c is ∼ 35 ps, requiring a track time-resolution of 15 ps for their clean separation. Expecting 30 detected photons per particle, this requires a single-photon timing resolution of 70 ps
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