毫電荷粒子之研究及偵測

Abstract

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In this thesis, we study hypothetical millicharged particles (mCPs) predicted by extensions of the Standard Model involving hidden sector gauge symmetries, particularly via kinetic mixing with a dark $U(1)$. While their interactions with ordinary matter are extremely weak, mCPs may constitute a component of dark matter and gradually accumulate inside the Earth through gravitational trapping and thermal diffusion. Our study reviews the theoretical motivation for mCPs, their potential terrestrial accumulation, and proposes a novel method for their detection.We explore the use of a laser-based Mach-Zehnder interferometer (MZI) to probe the presence of mCPs via the phase shift induced in one optical arm traversing a high-density underground region. By leveraging quantum-enhanced measurement techniques, including homodyne detection and squeezed states, the sensitivity to weak phase shifts can be significantly improved. Our analysis shows that this interferometric scheme is capable of probing the effective electric charge of mCPs at levels far beyond current experimental limits. For mCP masses above $1 ext{GeV}$, the proposed method offers sensitivity to kinetic mixing parameters as small as $epsilon sim 10^{-13}$ , improving upon existing collider and astrophysical bounds by several orders of magnitude.