New Constraint on Dark Photon at T2K Off-Axis Near Detector

TL;DR

This paper evaluates the ND280 detector at T2K for detecting dark photons, demonstrating its potential to exclude new parameter regions and enhance searches for dark sector particles in future experiments.

Contribution

It presents the first detailed study of ND280's capability to search for dark photons produced in meson decays and bremsstrahlung, expanding the experimental reach.

Findings

Ten-year T2K operation can exclude unexplored dark photon parameters.

ND280 can probe broader parameter regions for dark photons and U(1)$_{B-L}$ gauge bosons.

Future T2K runs will significantly improve dark photon search sensitivity.

Abstract

The T2K experiment is one of the most powerful long-baseline experiments to investigate neutrino oscillations. The off-axis near detector called ND280 is installed 280 m downstream from the neutrino production target to measure the neutrino energy spectrum. In this paper, we study the capability of the ND280 detector to search for the dark photon produced through the meson rare decay and proton bremsstrahlung processes at the proton beam dump. We find that the ten-year operation of T2K with the ND280 detector excludes the unexplored parameter region for the dark photon mass and kinetic mixing. We also show that a broader parameter region can be searched by the ND280 in the future T2K operation for dark photon as well as U(1)$_{B-L}$ gauge boson.