Time resolution of time-of-flight detector based on multiple scintillation counters readout by SiPMs

TL;DR

This paper demonstrates that using multiple scintillation counters read out by SiPMs can achieve a time resolution of around 26 ps for 50 MeV/c positrons, supporting the design goals of the MEG II experiment.

Contribution

The work provides experimental validation of the time resolution achievable with prototype counters for positron detection in the MEG II experiment.

Findings

Time resolution improves with the square root of the number of counters.

Achieved time resolution of 26.2 ps with eight counters and Hamamatsu SiPMs.

Prototype counters meet the targeted timing performance for MEG II.

Abstract

A new timing detector measuring ~50 MeV/c positrons is under development for the MEG II experiment, aiming at a time resolution $\sigma_t \sim 30~\mathrm{ps}$. The resolution is expected to be achieved by measuring each positron time with multiple counters made of plastic scintillator readout by silicon photomultipliers (SiPMs). The purpose of this work is to demonstrate the time resolution for ~50 MeV/c positrons using prototype counters. Counters with dimensions of $90\times 40\times 5~\mathrm{mm}^3$ readout by six SiPMs (three on each $40\times 5~\mathrm{mm}^2$ plane) were built with SiPMs from Hamamatsu Photonics and AdvanSiD and tested in a positron beam at the DA$\Phi$NE Beam Test Facility. The time resolution was found to improve nearly as the square root of the number of counter hits. A time resolution $\sigma_t=26.2\pm1.3~\mathrm{ps}$ was obtained with eight counters with Hamamatsu SiPMs. These results suggest that the design resolution is achievable in the MEG II experiment.