A Laboratory Test of the U-Cell Model: Photoelectric Asymmetry from Substrate Rest-Frame Coupling

The U-Cell Model (UCM) predicts that the substrate lattice has a preferred rest frame, through which the Earth moves at v_eff ≈ 171 km/s. This preferred frame produces a measurable asymmetry in the photoelectric effect across a horizontal thin gold plate, with signal formula A ≈ 2 c_TZ E_kin/(hν), where c_TZ = (v_eff/c)(E_kin/E_Lambda)^2 and E_Lambda = 23.9 eV. At hν = 8.0 eV the predicted asymmetry is A ≈ 6.2×10^-7 at signal-to-noise ratio 27. Four independent falsification conditions — E_kin^2 energy scaling, 9% annual modulation of known phase (maximum in June), vanishing asymmetry for a vertical plate, and sign reversal in the flip test — distinguish a genuine UCM signal from all known systematic errors including surface asymmetry, intensity imbalance, and contact potential drift. Lock-in detection at two modulation frequencies separates the two photoemission channels to better than 10^-4 intensity matching. The experiment requires only a standard UV laser laboratory; estimated cost is 56,000–115,000 EUR over a 24-month programme. This is the only UCM prediction testable in the laboratory without astronomical infrastructure, and it is falsifiable within 24 months of operation. The same energy scale E_Lambda = 23.9 eV governs the MDAR acceleration scale g†, the dark energy fraction Omega_Lambda, and the dark matter threshold — all confirmed to sub-percent accuracy by astronomical observations.