Dark photon dark matter constraints at the Taiwan axion search experiment with haloscope

TL;DR

Re-analyzing data from the Taiwan Axion Search Experiment with Haloscope, this study sets new constraints on dark photon dark matter, emphasizing the importance of timing information and discussing a potential signal excess.

Contribution

The paper provides the first world-leading constraints on dark photon parameters from TASEH data, surpassing naive rescaling limits and highlighting the significance of timing analysis.

Findings

Excluded $||  2 imes 10^{-14}$ in the 19.46-19.84 μeV mass range

Identified a tentative 4.7σ excess at 19.5 μeV that is inconsistent with recent experiments

Showed that timing information is crucial for accurate dark photon constraints

Abstract

The dark photon is a well motivated candidate for the dark matter which comprises most of the mass of our visible Universe, leading to worldwide experimental and observational efforts towards its discovery. A primary tool in this search is the cavity haloscope, which facilitates resonantly enhanced conversion to photons from both dark photons and axions. In this context, limits from axion search experiments are often directly converted into dark photon constraints, without re-analyzing the original data. However, this rescaling may not fully capture all of the relevant physics due to various reasons. By re-examining data taken by the Taiwan Axion Search Experiment with Haloscope (TASEH) experiment, we derive a world-leading constraint on the dark photon parameter space, excluding $|\epsilon|\gtrsim2\times10^{-14}$ in the $19.46 - 19.84\,\mu$eV mass range, which exceeds the na{\"i}ve `rescaling limit' by roughly a factor of two. We emphasize that accounting for the scanning timing information is crucial for deriving limits for the polarized dark photon case. In the data, we also analyze a tentative signal excess with a local significance of 4.7$\sigma$ ($m_X \simeq 19.5\,\mu$eV) that persists in the absence of a magnetic field. While this excess mimics the behavior of a dark photon signal, it has been excluded by recent results from the HAYSTAC and ORGAN-Q experiments. This case study, nevertheless, highlights the risk of discarding valid dark photon signals when relying on axion-specific magnetic field vetoes.