Performance of the High-Angle Time Projection Chambers in the Upgraded T2K Off-Axis Near Detector

TL;DR

This paper details the upgrade of the T2K off-axis near detector with new Time Projection Chambers that utilize resistive Micromegas technology, improving spatial resolution and particle identification for enhanced experimental precision.

Contribution

Introduction of innovative resistive Micromegas TPCs with detailed system descriptions and performance testing in neutrino and cosmic ray environments.

Findings

Improved spatial resolution of the new TPCs

Enhanced particle identification capabilities

Successful operation and data collection in neutrino beams

Abstract

The off-axis magnetic near detector of the T2K experiment has undergone a significant upgrade, including the construction and installation of two new Time Projection Chambers featuring innovative resistive Micromegas technology and a field cage composed of thin composite walls. This paper provides a detailed description of the new components of the chambers, including the gas system, gas monitoring chambers, and data acquisition system. Additionally, it reports the results of extensive testing using both neutrino beams and cosmic rays, with comparisons between data and Monte Carlo simulations. The new detectors achieve improved spatial resolution and enhanced particle identification capabilities which are crucial for the precision goals of the T2K experiment.