Sensitivity Windows for Yukawa-Type Residuals in Fixed-Gap Casimir Cavities: From Residual Discrimination Mapping to Experimental Bounds

This paper computes the minimum detectable Yukawa coupling αmin(λ) for the Au/doped-Si fixed-gap Casimir residual protocol under three systematic-floor scenarios: conservative (0.5%), realistic (0.2%), and optimistic (0.05%). Building on the residual discrimination mapping framework developed in previous work, the paper introduces a benchmark ratio r = αmin/αChen, where αChen(λ) is derived from the experimental constraint reported by Chen et al. (PRL 2016). The ratio provides a direct measure of whether a fixed-gap residual protocol reaches benchmark-level sensitivity within a given interaction range and systematic-floor scenario. The analysis identifies sensitivity windows in the 50–300 nm range and quantifies the systematic-floor requirements needed for a fixed-gap Casimir platform to become experimentally meaningful. The conservative floor remains above benchmark sensitivity throughout the investigated range. The realistic floor reaches benchmark-level sensitivity only in a narrow upper window, while the optimistic floor substantially extends the accessible region. The work does not present new exclusion limits. Instead, it provides a methodological sensitivity study and a quantitative bridge between residual discrimination mapping and future experimental implementations. Supplementary code and numerical data are included to reproduce the sensitivity-band figures, benchmark-ratio analysis, required-floor calculations, and numerical tables.