Physics and Performance of the Upgraded T2K’s Near Detector

Abstract

Tokai-to-Kamioka (T2K) is a long-baseline neutrino oscillation experiment currently ongoing in Japan. T2K has been the first experiment to detect the appearance of electron neutrinos in a muon neutrino beam and is now heading towards a quantification of the CP violating phase in the leptonic sector. This study requires to measure precisely the appearance probabilities of both neutrino and antineutrinos. Understanding the systematic uncertainties is essential to achieve such a challenge, thus the collaboration has decided to upgrade T2K’s near detector: ND280. The upgrade consists in the addition of a highly segmented plastic scintillator target named super fine-grained detector (SFGD) surrounded with two horizontal TPCs (HA-TPC) equipped with resistive MicroMegas modules which aim at covering the tracking of particles having high angles with respect to the beam line. In addition, six time-of-flight (ToF) planes will surround the new sub-detectors. These upgrades are currently being constructed and will be installed by the end of 2022. Ultimately, the upgraded detector will enlarge the phase space by providing constraints with a new variety of variables such as transverse kinematic imbalance which are more sensitive to nuclear effects, and thus will allow to constrain T2K’s dominant systematics with unprecedented accuracy.